javax.swing.text.BadLocationException: Length must be positive
   at javax.swing.text.AbstractDocument.getText(AbstractDocument.java:795)
Caused: java.lang.IllegalStateException: javax.swing.text.BadLocationException: Length must be positive
   at org.netbeans.editor.FixLineSyntaxState.fixSyntaxStateInfos(FixLineSyntaxState.java:524)
   at org.netbeans.editor.FixLineSyntaxState.update(FixLineSyntaxState.java:303)
   at org.netbeans.editor.FixLineSyntaxState$BeforeLineUndo.undo(FixLineSyntaxState.java:611)
   at org.netbeans.editor.BaseDocumentEvent.undo(BaseDocumentEvent.java:289)
   at org.netbeans.editor.GuardedDocumentEvent.undo(GuardedDocumentEvent.java:72)
   at javax.swing.undo.CompoundEdit.undo(CompoundEdit.java:46)
   at org.netbeans.editor.BaseDocument$AtomicCompoundEdit.undo(BaseDocument.java:2204)
   at javax.swing.undo.UndoManager.undoTo(UndoManager.java:320)
   at javax.swing.undo.UndoManager.undo(UndoManager.java:398)
   at org.openide.awt.UndoRedo$Manager.undo(UndoRedo.java:184)
   at org.openide.text.CloneableEditorSupport$UndoGroupManager.undo(CloneableEditorSupport.java:3704)
   at org.openide.text.CloneableEditorSupport$CESUndoRedoManager.access$3301(CloneableEditorSupport.java:3235)
   at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.run(CloneableEditorSupport.java:3408)
   at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:314)
   at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3384)
   at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3375)
   at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3371)
   at org.openide.text.CloneableEditorSupport$CESUndoRedoManager.undo(CloneableEditorSupport.java:3268)
   at org.netbeans.core.multiview.MultiViewPeer$DelegateUndoRedo.undo(MultiViewPeer.java:788)
   at org.openide.actions.UndoAction.performAction(UndoAction.java:185)
   at org.openide.util.actions.CallableSystemAction$1.run(CallableSystemAction.java:129)
   at org.openide.util.actions.ActionInvoker$1.run(ActionInvoker.java:95)
   at org.openide.util.actions.ActionInvoker.doPerformAction(ActionInvoker.java:116)
   at org.openide.util.actions.ActionInvoker.invokeAction(ActionInvoker.java:99)
   at org.openide.util.actions.CallableSystemAction.actionPerformed(CallableSystemAction.java:126)
   at org.netbeans.modules.editor.NbEditorKit$NbUndoAction.actionPerformed(NbEditorKit.java:569)
   at org.netbeans.editor.BaseAction.actionPerformed(BaseAction.java:339)
   at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1639)
   at javax.swing.JComponent.processKeyBinding(JComponent.java:2851)
   at javax.swing.JComponent.processKeyBindings(JComponent.java:2886)
   at javax.swing.JComponent.processKeyEvent(JComponent.java:2814)
   at java.awt.Component.processEvent(Component.java:6065)
   at java.awt.Container.processEvent(Container.java:2041)
   at java.awt.Component.dispatchEventImpl(Component.java:4651)
   at java.awt.Container.dispatchEventImpl(Container.java:2099)
   at java.awt.Component.dispatchEvent(Component.java:4481)
   at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1850)
   at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:712)
   at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:990)
   at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:855)
   at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:676)
   at java.awt.Component.dispatchEventImpl(Component.java:4523)
   at java.awt.Container.dispatchEventImpl(Container.java:2099)
   at java.awt.Window.dispatchEventImpl(Window.java:2478)
   at java.awt.Component.dispatchEvent(Component.java:4481)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:643)
   at java.awt.EventQueue.access$000(EventQueue.java:84)
   at java.awt.EventQueue$1.run(EventQueue.java:602)
   at java.awt.EventQueue$1.run(EventQueue.java:600)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
   at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
   at java.awt.EventQueue$2.run(EventQueue.java:616)
   at java.awt.EventQueue$2.run(EventQueue.java:614)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:613)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:153)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)