NullPointerException in DashboardPanel when collapsing widget

[jchappelle]

Every now and then I get an error when clicking the collapse link. Below is the stack trace. It looks like the transient DashboardContext is null. I had a chrome browser and an IE 11 browser up and it was happening with both at the same time.

java.lang.NullPointerException
at ro.fortsoft.wicket.dashboard.web.DashboardPanel.onWidgetsSorted(DashboardPanel.java:100)
at ro.fortsoft.wicket.dashboard.web.DashboardPanel.onEvent(DashboardPanel.java:76)
at org.apache.wicket.settings.def.FrameworkSettings.dispatchEvent(FrameworkSettings.java:132)
at org.apache.wicket.ComponentEventSender.dispatchToComponent(ComponentEventSender.java:282)
at org.apache.wicket.ComponentEventSender.access$100(ComponentEventSender.java:36)
at org.apache.wicket.ComponentEventSender$ComponentEventVisitor.component(ComponentEventSender.java:329)
at org.apache.wicket.ComponentEventSender$ComponentEventVisitor.component(ComponentEventSender.java:306)
at org.apache.wicket.util.visit.Visits.visitChildren(Visits.java:144)
at org.apache.wicket.util.visit.Visits.visitChildren(Visits.java:162)
at org.apache.wicket.util.visit.Visits.visitChildren(Visits.java:123)
at org.apache.wicket.util.visit.Visits.visitChildren(Visits.java:192)
at org.apache.wicket.MarkupContainer.visitChildren(MarkupContainer.java:875)
at org.apache.wicket.ComponentEventSender.breadth(ComponentEventSender.java:160)
at org.apache.wicket.ComponentEventSender.send(ComponentEventSender.java:68)
at org.apache.wicket.Component.send(Component.java:4429)
at ro.fortsoft.wicket.dashboard.web.DashboardColumnPanel$2.onSort(DashboardColumnPanel.java:109)
at ro.fortsoft.wicket.dashboard.web.SortableAjaxBehavior.respond(SortableAjaxBehavior.java:59)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:633)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:258)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:241)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:250)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:236)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:862)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:201)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:282)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1291)
at org.springframework.orm.hibernate4.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:152)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1291)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:443)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:556)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:227)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1044)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:372)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:189)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:978)
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:369)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:486)
at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:933)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:995)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:644)
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:668)
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:744)

Complete stack:

org.apache.wicket.WicketRuntimeException: Method onRequest of interface org.apache.wicket.behavior.IBehaviorListener targeted at ro.fortsoft.wicket.dashboard.web.DashboardColumnPanel$2@16a626b2 on component [WebMarkupContainer [Component id = columnContainer]] threw an exception
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:268)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:241)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:250)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:236)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:862)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)

java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor177.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:258)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:241)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:250)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:236)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:862)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)

[jchappelle]

This seems to only happen when I try to sort after clicking the DetachAction. I'm able to make it happen in the demo sometimes but in my custom application all the time.