Exception logged in Error Log from occurrence marking

I'm not sure, but presumably this occurred when the selection changed in the source editor (I just happened to still have "Mark Occurrences" mode on).

Error obtaining occurrences of selected node
java.lang.NullPointerException
at org.eclipse.imp.x10dt.ui.editor.X10OccurrenceIdentifier.getProcInstance(X10OccurrenceIdentifier.java:114)
at org.eclipse.imp.x10dt.ui.editor.X10OccurrenceIdentifier.getOccurrencesOf(X10OccurrenceIdentifier.java:69)
at org.eclipse.imp.editor.MarkOccurrencesAction.recomputeAnnotationsForSelection(MarkOccurrencesAction.java:303)
at org.eclipse.imp.editor.MarkOccurrencesAction.setUpActiveEditor(MarkOccurrencesAction.java:431)
at org.eclipse.imp.editor.MarkOccurrencesAction.access$0(MarkOccurrencesAction.java:410)
at org.eclipse.imp.editor.MarkOccurrencesAction$EditorPartListener.partActivated(MarkOccurrencesAction.java:113)
at org.eclipse.ui.internal.PartListenerList$1.run(PartListenerList.java:72)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.runtime.Platform.run(Platform.java:888)
at org.eclipse.ui.internal.PartListenerList.fireEvent(PartListenerList.java:57)
at org.eclipse.ui.internal.PartListenerList.firePartActivated(PartListenerList.java:70)
at org.eclipse.ui.internal.PartService.firePartActivated(PartService.java:187)
at org.eclipse.ui.internal.PartService.setActivePart(PartService.java:306)
at org.eclipse.ui.internal.WorkbenchPagePartList.fireActivePartChanged(WorkbenchPagePartList.java:57)
at org.eclipse.ui.internal.PartList.setActivePart(PartList.java:136)
at org.eclipse.ui.internal.WorkbenchPage.setActivePart(WorkbenchPage.java:3531)
at org.eclipse.ui.internal.WorkbenchPage.requestActivation(WorkbenchPage.java:3071)
at org.eclipse.ui.internal.PartPane.requestActivation(PartPane.java:279)
at org.eclipse.ui.internal.EditorPane.requestActivation(EditorPane.java:98)
at org.eclipse.ui.internal.PartPane.handleEvent(PartPane.java:237)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:3542)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1247)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1270)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1251)
at org.eclipse.swt.widgets.Shell.setActiveControl(Shell.java:1235)
at org.eclipse.swt.widgets.Control.sendFocusEvent(Control.java:2865)
at org.eclipse.swt.widgets.Canvas.sendFocusEvent(Canvas.java:62)
at org.eclipse.swt.widgets.Display.checkFocus(Display.java:578)
at org.eclipse.swt.widgets.Shell.makeFirstResponder(Shell.java:1006)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:4756)
at org.eclipse.swt.internal.cocoa.OS.objc_msgSendSuper(Native Method)
at org.eclipse.swt.widgets.Widget.callSuper(Widget.java:202)
at org.eclipse.swt.widgets.Widget.windowSendEvent(Widget.java:1750)
at org.eclipse.swt.widgets.Shell.windowSendEvent(Shell.java:1821)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:4712)
at org.eclipse.swt.internal.cocoa.OS.objc_msgSendSuper(Native Method)
at org.eclipse.swt.widgets.Display.applicationSendEvent(Display.java:4284)
at org.eclipse.swt.widgets.Display.applicationProc(Display.java:4351)
at org.eclipse.swt.internal.cocoa.OS.objc_msgSend(Native Method)
at org.eclipse.swt.internal.cocoa.NSApplication.sendEvent(NSApplication.java:101)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3096)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:592)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
at org.eclipse.equinox.launcher.Main.main(Main.java:1287)