Nullpointer in init when trying to upgrade old scheduler jobs containing null object

2010-02-05 17:08:02,969 [http://xwiki.ludovic.org/xwiki/bin/view/Main/Dashboard?viewer=attachments] ERROR plugin.XWikiPluginManager 
      - Cannot initialize plugin [com.xpn.xwiki.plugin.scheduler.SchedulerPlugin]. This plugin will not be available. 
java.lang.NullPointerException
	at com.xpn.xwiki.plugin.scheduler.SchedulerPlugin.restoreExistingJobs(SchedulerPlugin.java:276)
	at com.xpn.xwiki.plugin.scheduler.SchedulerPlugin.init(SchedulerPlugin.java:132)
	at com.xpn.xwiki.plugin.XWikiPluginManager.initPlugin(XWikiPluginManager.java:155)
	at com.xpn.xwiki.plugin.XWikiPluginManager.addPlugin(XWikiPluginManager.java:92)
	at com.xpn.xwiki.plugin.XWikiPluginManager.addPlugins(XWikiPluginManager.java:120)
	at com.xpn.xwiki.XWiki.preparePlugins(XWiki.java:1077)
	at com.xpn.xwiki.XWiki.initXWiki(XWiki.java:768)
	at com.xpn.xwiki.XWiki.<init>(XWiki.java:699)
	at com.xpn.xwiki.XWiki.getMainXWiki(XWiki.java:336)
	at com.xpn.xwiki.XWiki.getXWiki(XWiki.java:417)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:135)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:115)
	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:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.xpn.xwiki.wysiwyg.server.filter.ConversionFilter.doFilter(ConversionFilter.java:152)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:118)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.xpn.xwiki.plugin.webdav.XWikiDavFilter.doFilter(XWikiDavFilter.java:68)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.xpn.xwiki.web.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:295)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:112)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
	at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
	at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
	at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:769)
	at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:698)
	at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:891)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
	at java.lang.Thread.run(Thread.java:619)