Sometimes on 'page refresh' Applications panel gives a velocity error

org.xwiki.rendering.macro.MacroExecutionException: Failed to evaluate Velocity Macro for content [#set($discard = $xwiki.ssx.use('Panels.Applications'))
#set($discard = $xwiki.jsx.use('Panels.Applications'))
#panelheader($services.localization.render('panels.applications.title'))
#foreach($uix in $services.uix.getExtensions('org.xwiki.platform.panels.Applications', {'sortByParameter' : 'label'}))
  #set($params = $uix.getParameters())
  #if($"$!params.icon" != '' && "$!params.label" != '' && "$!params.target" != '' && $xwiki.hasAccessLevel('view', $xcontext.user, $params.target))
(% class="applicationsPanel" %)
* [[image:$params.icon $params.label>>$params.target]]
  #end
#end
#if($xwiki.hasWikiAdminRights())
## We need the 3 newlines below to have a separation between the lists



(% class="applicationsPanel" %)
* [[image:icon:add $services.localization.render('panels.applications.more')>>XWiki.XWikiPreferences||class="applicationPanelMoreButton" queryString="editor=globaladmin&section=XWiki.AddExtensions"]]

(% class="applicationPanelMoreContainer hidden" %)(((
(% class="applicationsPanel" %)
#foreach($uix in $services.uix.getExtensions('org.xwiki.platform.panels.Applications.more', {'sortByParameter' : 'label'}))
  #set($params = $uix.getParameters())
  #if($"$!params.icon" != '' && "$!params.label" != '' && "$!params.target" != '')
(% class="applicationsPanel" %)
* [[image:$params.icon $params.label>>$params.target]]
  #end
#end
)))
#end
#panelfooter()]
	at org.xwiki.rendering.internal.macro.velocity.VelocityMacro.evaluateString(VelocityMacro.java:131)
	at org.xwiki.rendering.internal.macro.velocity.VelocityMacro.evaluateString(VelocityMacro.java:50)
	at org.xwiki.rendering.macro.script.AbstractScriptMacro.evaluateBlock(AbstractScriptMacro.java:302)
	at org.xwiki.rendering.macro.script.AbstractScriptMacro.execute(AbstractScriptMacro.java:198)
	at org.xwiki.rendering.macro.script.AbstractScriptMacro.execute(AbstractScriptMacro.java:59)
	at org.xwiki.rendering.internal.transformation.macro.MacroTransformation.transformOnce(MacroTransformation.java:191)
	at org.xwiki.rendering.internal.transformation.macro.MacroTransformation.transform(MacroTransformation.java:132)
	at org.xwiki.panels.internal.PanelWikiUIExtension.execute(PanelWikiUIExtension.java:150)
	at sun.reflect.GeneratedMethodAccessor262.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:395)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:384)
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:173)
	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
	at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:567)
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:151)
	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
	at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:369)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
	at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:420)
	at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:228)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:187)
	at com.xpn.xwiki.render.XWikiVelocityRenderer.evaluate(XWikiVelocityRenderer.java:105)
	at com.xpn.xwiki.internal.template.DefaultPrivilegedTemplateRenderer.evaluate(DefaultPrivilegedTemplateRenderer.java:125)
	at com.xpn.xwiki.internal.template.DefaultPrivilegedTemplateRenderer.evaluateTemplate(DefaultPrivilegedTemplateRenderer.java:75)
	at com.xpn.xwiki.XWiki.evaluateTemplate(XWiki.java:1841)
	at com.xpn.xwiki.XWiki.parseTemplate(XWiki.java:1781)
	at com.xpn.xwiki.api.XWiki.parseTemplate(XWiki.java:918)
	at sun.reflect.GeneratedMethodAccessor174.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:395)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:384)
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:173)
	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
	at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:369)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
	at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:216)
	at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:311)
	at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:230)
	at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:228)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:187)
	at com.xpn.xwiki.render.XWikiVelocityRenderer.evaluate(XWikiVelocityRenderer.java:105)
	at com.xpn.xwiki.internal.template.DefaultPrivilegedTemplateRenderer.evaluate(DefaultPrivilegedTemplateRenderer.java:125)
	at com.xpn.xwiki.internal.template.DefaultPrivilegedTemplateRenderer.evaluateTemplate(DefaultPrivilegedTemplateRenderer.java:75)
	at com.xpn.xwiki.XWiki.evaluateTemplate(XWiki.java:1841)
	at com.xpn.xwiki.XWiki.parseTemplate(XWiki.java:1781)
	at com.xpn.xwiki.api.XWiki.parseTemplate(XWiki.java:918)
	at sun.reflect.GeneratedMethodAccessor174.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:395)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:384)
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:173)
	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
	at org.apache.velocity.runtime.parser.node.ASTReference.render(ASTReference.java:369)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
	at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:216)
	at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:311)
	at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:230)
	at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:106)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:228)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:187)
	at com.xpn.xwiki.render.XWikiVelocityRenderer.evaluate(XWikiVelocityRenderer.java:105)
	at com.xpn.xwiki.internal.template.DefaultPrivilegedTemplateRenderer.evaluate(DefaultPrivilegedTemplateRenderer.java:125)
	at com.xpn.xwiki.internal.template.DefaultPrivilegedTemplateRenderer.evaluateTemplate(DefaultPrivilegedTemplateRenderer.java:75)
	at com.xpn.xwiki.XWiki.evaluateTemplate(XWiki.java:1841)
	at com.xpn.xwiki.web.Utils.parseTemplate(Utils.java:166)
	at com.xpn.xwiki.web.Utils.parseTemplate(Utils.java:88)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:300)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:128)
	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:735)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
	at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:669)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1448)
	at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:121)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419)
	at org.xwiki.wysiwyg.server.filter.ConversionFilter.doFilter(ConversionFilter.java:144)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419)
	at com.xpn.xwiki.plugin.webdav.XWikiDavFilter.doFilter(XWikiDavFilter.java:66)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419)
	at org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:208)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419)
	at org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:111)
	at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1419)
	at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:455)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
	at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557)
	at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
	at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1075)
	at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:384)
	at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
	at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1009)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
	at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255)
	at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154)
	at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
	at org.eclipse.jetty.server.Server.handle(Server.java:368)
	at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:488)
	at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:932)
	at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:994)
	at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:640)
	at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
	at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
	at java.lang.Thread.run(Thread.java:680)
Caused by: org.xwiki.velocity.XWikiVelocityException: Failed to evaluate content with id [xwiki:Panels.Applications]
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:247)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:187)
	at org.xwiki.rendering.internal.macro.velocity.VelocityMacro.evaluateString(VelocityMacro.java:124)
	... 125 more
Caused by: org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getExtensions' in  class org.xwiki.uiextension.internal.scripting.UIExtensionScriptService threw exception java.lang.NullPointerException at xwiki:Panels.Applications[line 4, column 32]
	at org.apache.velocity.runtime.parser.node.ASTMethod.handleInvocationException(ASTMethod.java:243)
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:187)
	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
	at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:567)
	at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:318)
	at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
	at org.xwiki.velocity.internal.DefaultVelocityEngine.evaluate(DefaultVelocityEngine.java:228)
	... 127 more
Caused by: java.lang.NullPointerException
	at org.xwiki.uiextension.internal.filter.SortByParameterFilter$UIExtensionParameterComparator.compare(SortByParameterFilter.java:88)
	at org.xwiki.uiextension.internal.filter.SortByParameterFilter$UIExtensionParameterComparator.compare(SortByParameterFilter.java:52)
	at java.util.Arrays.mergeSort(Arrays.java:1270)
	at java.util.Arrays.sort(Arrays.java:1210)
	at java.util.Collections.sort(Collections.java:157)
	at org.xwiki.uiextension.internal.filter.SortByParameterFilter.filter(SortByParameterFilter.java:111)
	at org.xwiki.uiextension.internal.scripting.UIExtensionScriptService.getExtensions(UIExtensionScriptService.java:136)
	at sun.reflect.GeneratedMethodAccessor273.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:395)
	at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:384)
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:173)
	... 133 more