Error while opening content should be catched and transformed to a more readable solution instruction

Somehow a content in my wiki is producing the following error when I try to open it.

Error number 4001 in 4: Error while parsing velocity page Wrapped Exception: Invocation of method 'parseContent' in class com.xpn.xwiki.api.XWiki threw exception java.lang.NullPointerException @ [14,16]

${doc.displayTitle}

$doc.web: ${pdoc.displayTitle} > $doc.displayTitle
$msg.get("menu")
$msg.get("core.menu.documentation")
$msg.get("core.menu.view"): $msg.get("core.menu.view.comments") $msg.get("core.menu.view.attachments") $msg.get("core.menu.view.history")
$msg.get("print"): $msg.get("preview") $msg.get("pdf") $msg.get("rtf")
$msg.get("problemoccured")

$msg.get("detailedinformation"):

Error number 3202 in 3: Exception while reading document People.Ralf Kahrl
Wrapped Exception: Error number 3212 in 3: Exception while loading object

{0} of class {1} and number {2}
Wrapped Exception: Error number 3212 in 3: Exception while loading object {0}

of class

{1}, number {2} and property {3}
Wrapped Exception: Error number 3212 in 3: Exception while loading property tags of object People.Ralf Kahrl
Wrapped Exception: a different object with the same identifier value was already associated with the session: [com.xpn.xwiki.objects.DBStringListProperty#


]
com.xpn.xwiki.XWikiException: Error number 3202 in 3: Exception while reading document People.Ralf Kahrl
Wrapped Exception: Error number 3212 in 3: Exception while loading object {0} of class {1}

and number

{2}
Wrapped Exception: Error number 3212 in 3: Exception while loading object {0} of class {1}, number {2}

and property

{3}
Wrapped Exception: Error number 3212 in 3: Exception while loading property tags of object People.Ralf Kahrl
Wrapped Exception: a different object with the same identifier value was already associated with the session: [com.xpn.xwiki.objects.DBStringListProperty#


]
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiDoc(XWikiHibernateStore.java:452)
at com.xpn.xwiki.store.XWikiCacheStore.loadXWikiDoc(XWikiCacheStore.java:160)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:956)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:990)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:3824)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:134)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:868)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:663)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)


Wrapped Exception:

com.xpn.xwiki.XWikiException: Error number 3212 in 3: Exception while loading object {0} of class {1} and number {2}
Wrapped Exception: Error number 3212 in 3: Exception while loading object {0} of class {1}, number {2} and property {3}

Wrapped Exception: Error number 3212 in 3: Exception while loading property tags of object People.Ralf Kahrl
Wrapped Exception: a different object with the same identifier value was already associated with the session: [com.xpn.xwiki.objects.DBStringListProperty#

]
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiCollection(XWikiHibernateStore.java:787)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiDoc(XWikiHibernateStore.java:425)
at com.xpn.xwiki.store.XWikiCacheStore.loadXWikiDoc(XWikiCacheStore.java:160)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:956)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:990)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:3824)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:134)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:868)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:663)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)

Wrapped Exception:

com.xpn.xwiki.XWikiException: Error number 3212 in 3: Exception while loading object

{0}

of class

{1}

, number

{2}

and property

{3}

Wrapped Exception: Error number 3212 in 3: Exception while loading property tags of object People.Ralf Kahrl
Wrapped Exception: a different object with the same identifier value was already associated with the session: [com.xpn.xwiki.objects.DBStringListProperty#

]
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiCollection(XWikiHibernateStore.java:774)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiDoc(XWikiHibernateStore.java:425)
at com.xpn.xwiki.store.XWikiCacheStore.loadXWikiDoc(XWikiCacheStore.java:160)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:956)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:990)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:3824)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:134)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:868)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:663)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)

Wrapped Exception:

com.xpn.xwiki.XWikiException: Error number 3212 in 3: Exception while loading property tags of object People.Ralf Kahrl
Wrapped Exception: a different object with the same identifier value was already associated with the session: [com.xpn.xwiki.objects.DBStringListProperty#

]
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiProperty(XWikiHibernateStore.java:916)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiCollection(XWikiHibernateStore.java:743)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiDoc(XWikiHibernateStore.java:425)
at com.xpn.xwiki.store.XWikiCacheStore.loadXWikiDoc(XWikiCacheStore.java:160)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:956)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:990)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:3824)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:134)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:868)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:663)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)

Wrapped Exception:

org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.xpn.xwiki.objects.DBStringListProperty#

]
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:132)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:177)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:87)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:891)
at org.hibernate.impl.SessionImpl.load(SessionImpl.java:799)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiProperty(XWikiHibernateStore.java:893)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiCollection(XWikiHibernateStore.java:743)
at com.xpn.xwiki.store.XWikiHibernateStore.loadXWikiDoc(XWikiHibernateStore.java:425)
at com.xpn.xwiki.store.XWikiCacheStore.loadXWikiDoc(XWikiCacheStore.java:160)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:956)
at com.xpn.xwiki.XWiki.getDocument(XWiki.java:990)
at com.xpn.xwiki.XWiki.prepareDocuments(XWiki.java:3824)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:134)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:868)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:663)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)