javax.swing.undo.CannotUndoException
        at javax.swing.undo.AbstractUndoableEdit.undo(AbstractUndoableEdit.java:93)
        at javax.swing.undo.CompoundEdit.undo(CompoundEdit.java:42)
        at org.netbeans.editor.BaseDocument$AtomicCompoundEdit.undo(BaseDocument.java:2181)
        at org.openide.text.CloneableEditorSupport$FilterUndoableEdit.undo(CloneableEditorSupport.java:2981)
        at org.openide.text.CloneableEditorSupport$BeforeModificationEdit.undo(CloneableEditorSupport.java:3141)
        at javax.swing.undo.UndoManager.undoTo(UndoManager.java:320)
        at javax.swing.undo.UndoManager.undo(UndoManager.java:398)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager.access$3201(CloneableEditorSupport.java:3174)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.run(CloneableEditorSupport.java:3337)
        at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:327)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3317)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3309)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager.undo(CloneableEditorSupport.java:3207)
        at org.netbeans.modules.visualweb.insync.UndoEvent.undo(UndoEvent.java:131)
        at org.netbeans.modules.visualweb.insync.UndoManager.undo(UndoManager.java:241)
        at org.netbeans.core.multiview.MultiViewPeer$DelegateUndoRedo.undo(MultiViewPeer.java:748)
        at org.openide.actions.UndoAction.performAction(UndoAction.java:177)
        at org.openide.util.actions.CallableSystemAction$1.run(CallableSystemAction.java:127)
        at org.netbeans.modules.openide.util.ActionsBridge.implPerformAction(ActionsBridge.java:83)
        at org.netbeans.modules.openide.util.ActionsBridge.doPerformAction(ActionsBridge.java:64)
        at org.openide.util.actions.CallableSystemAction.actionPerformed(CallableSystemAction.java:123)
        at org.openide.windows.TopComponent.processKeyBinding(TopComponent.java:1052)
        at javax.swing.JComponent.processKeyBindings(JComponent.java:2885)
        at javax.swing.JComponent.processKeyEvent(JComponent.java:2802)
        at java.awt.Component.processEvent(Component.java:6040)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4630)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        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:4502)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:125)
        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)