java.lang.NullPointerException: Invalid doc parameter. Document may not be null!
   at org.openide.text.NbDocument.checkDocParameter(NbDocument.java:476)
   at org.openide.text.NbDocument.createPosition(NbDocument.java:222)
   at org.openide.text.PositionRef$Manager$DocumentRenderer.run(PositionRef.java:992)
   at org.openide.text.PositionRef$Manager$DocumentRenderer.render(PositionRef.java:911)
   at org.openide.text.PositionRef$Manager$DocumentRenderer.renderToObject(PositionRef.java:929)
   at org.openide.text.PositionRef$Manager$Kind.toMemory(PositionRef.java:497)
   at org.openide.text.PositionRef$Manager$DocumentRenderer.run(PositionRef.java:1074)
   at org.openide.text.PositionRef$Manager$DocumentRenderer.render(PositionRef.java:911)
   at org.openide.text.PositionRef$Manager.processPositions(PositionRef.java:359)
   at org.openide.text.DocumentOpenClose$DocumentLoad.atomicLockedRun(DocumentOpenClose.java:773)
   at org.openide.text.DocumentOpenClose$DocumentLoad.run(DocumentOpenClose.java:613)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.NullPointerException: Invalid doc parameter. Document may not be null!
   at org.openide.util.RequestProcessor$Task.schedule(RequestProcessor.java:1464)
   at org.netbeans.modules.showtodos.TodoAnnotationProvider$ScanningListener.restartTimer(TodoAnnotationProvider.java:181)
   at org.netbeans.modules.showtodos.TodoAnnotationProvider$ScanningListener.change(TodoAnnotationProvider.java:177)
   at org.netbeans.modules.showtodos.TodoAnnotationProvider$ScanningListener.insertUpdate(TodoAnnotationProvider.java:147)
   at org.netbeans.lib.editor.util.swing.PriorityDocumentListenerList.insertUpdate(PriorityDocumentListenerList.java:85)
   at javax.swing.text.AbstractDocument.fireInsertUpdate(AbstractDocument.java:202)
   at org.netbeans.editor.BaseDocument.fireInsertUpdate(BaseDocument.java:1624)
   at org.netbeans.editor.BaseDocumentEvent.undo(BaseDocumentEvent.java:286)
   at org.netbeans.editor.GuardedDocumentEvent.undo(GuardedDocumentEvent.java:72)
   at org.netbeans.modules.editor.lib2.document.StableCompoundEdit.undo(StableCompoundEdit.java:93)
   at org.netbeans.editor.BaseDocument$AtomicCompoundEdit.undo(BaseDocument.java:2196)
   at org.netbeans.editor.BaseDocument.undoAtomicEdits(BaseDocument.java:2114)
   at org.netbeans.editor.BaseDocument.breakAtomicLock(BaseDocument.java:1800)
   at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:327)
   at org.openide.text.NbDocument.runAtomic(NbDocument.java:436)
   at org.openide.text.DocumentOpenClose$DocumentLoad.run(DocumentOpenClose.java:653)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)