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:2905)
        at org.openide.text.CloneableEditorSupport$BeforeModificationEdit.undo(CloneableEditorSupport.java:3065)
        at javax.swing.undo.UndoManager.undoTo(UndoManager.java:320)
        at javax.swing.undo.UndoManager.undo(UndoManager.java:398)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager.access$3201(CloneableEditorSupport.java:3098)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.run(CloneableEditorSupport.java:3259)
        at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:324)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3239)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager$RenderUndo.<init>(CloneableEditorSupport.java:3231)
        at org.openide.text.CloneableEditorSupport$CESUndoRedoManager.undo(CloneableEditorSupport.java:3131)
        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:745)
        at org.openide.actions.UndoAction.performAction(UndoAction.java:177)
        at org.openide.util.actions.CallableSystemAction$1.run(CallableSystemAction.java:118)
        at org.netbeans.modules.openide.util.ActionsBridge.doPerformAction(ActionsBridge.java:77)
        at org.openide.util.actions.CallableSystemAction.actionPerformed(CallableSystemAction.java:114)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:273)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
        at java.awt.Component.processMouseEvent(Component.java:6301)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at org.openide.awt.ToolbarButton.processMouseEvent(ToolbarButton.java:61)
        at java.awt.Component.processEvent(Component.java:6066)
        at java.awt.Container.processEvent(Container.java:2085)
        at java.awt.Component.dispatchEventImpl(Component.java:4667)
        at java.awt.Container.dispatchEventImpl(Container.java:2143)
        at java.awt.Component.dispatchEvent(Component.java:4497)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4600)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4264)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4194)
        at java.awt.Container.dispatchEventImpl(Container.java:2129)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4497)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:635)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)