java.lang.NullPointerException
   at org.netbeans.modules.editor.lib2.view.ViewUpdates.removeUpdate(ViewUpdates.java:285)
Caused: java.lang.reflect.InvocationTargetException
   at sun.reflect.GeneratedMethodAccessor52.invoke(GeneratedMethodAccessor52.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:601)
   at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:459)
Caused: java.lang.reflect.UndeclaredThrowableException
   at $Proxy22.removeUpdate(.java:0)
   at org.netbeans.lib.editor.util.swing.PriorityDocumentListenerList.removeUpdate(PriorityDocumentListenerList.java:116)
   at javax.swing.text.AbstractDocument.fireRemoveUpdate(AbstractDocument.java:260)
   at org.netbeans.editor.BaseDocument.fireRemoveUpdate(BaseDocument.java:1659)
   at org.netbeans.editor.BaseDocumentEvent.undo(BaseDocumentEvent.java:296)
   at org.netbeans.editor.GuardedDocumentEvent.undo(GuardedDocumentEvent.java:72)
   at javax.swing.undo.CompoundEdit.undo(CompoundEdit.java:63)
   at org.netbeans.editor.BaseDocument$AtomicCompoundEdit.undo(BaseDocument.java:2204)
   at org.netbeans.editor.BaseDocument.breakAtomicLock(BaseDocument.java:1860)
   at org.netbeans.editor.GuardedDocument.runAtomicAsUser(GuardedDocument.java:350)
   at org.netbeans.editor.BaseKit$InsertBreakAction.actionPerformed(BaseKit.java:1336)
   at org.netbeans.editor.BaseAction.actionPerformed(BaseAction.java:339)
   at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1661)
   at javax.swing.JComponent.processKeyBinding(JComponent.java:2879)
   at javax.swing.JComponent.processKeyBindings(JComponent.java:2926)
   at javax.swing.JComponent.processKeyEvent(JComponent.java:2842)
   at java.awt.Component.processEvent(Component.java:6281)
   at java.awt.Container.processEvent(Container.java:2229)
   at java.awt.Component.dispatchEventImpl(Component.java:4860)
   at java.awt.Container.dispatchEventImpl(Container.java:2287)
   at java.awt.Component.dispatchEvent(Component.java:4686)
   at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1908)
   at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:752)
   at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1017)
   at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:889)
   at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:717)
   at java.awt.Component.dispatchEventImpl(Component.java:4730)
   at java.awt.Container.dispatchEventImpl(Container.java:2287)
   at java.awt.Window.dispatchEventImpl(Window.java:2713)
   at java.awt.Component.dispatchEvent(Component.java:4686)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
   at java.awt.EventQueue.access$000(EventQueue.java:101)
   at java.awt.EventQueue$3.run(EventQueue.java:666)
   at java.awt.EventQueue$3.run(EventQueue.java:664)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
   at java.awt.EventQueue$4.run(EventQueue.java:680)
   at java.awt.EventQueue$4.run(EventQueue.java:678)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:153)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)