java.lang.AssertionError
        at org.netbeans.modules.javacore.JavaMetamodel.getFileObject(JavaMetamodel.java:189)
        at org.netbeans.modules.javacore.JavaMetamodel.getDataObject(JavaMetamodel.java:200)
        at org.netbeans.api.refactoring.RenameRefactoring$RenameDOElement.doRename(RenameRefactoring.java:819)
        at org.netbeans.api.refactoring.RenameRefactoring$RenameDOElement.undoExternalChange(RenameRefactoring.java:839)
        at org.netbeans.modules.javacore.UndoManager$ExternalUndoItem.undo(UndoManager.java:495)
        at org.netbeans.modules.javacore.UndoManager.undo(UndoManager.java:140)
        at org.netbeans.modules.refactoring.ui.UndoAction.actionPerformed(UndoAction.java:56)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786)
        at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1839)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
        at javax.swing.AbstractButton.doClick(AbstractButton.java:289)
        at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1113)
        at javax.swing.plaf.basic.BasicMenuItemUI$MouseInputHandler.mouseReleased(BasicMenuItemUI.java:943)
        at java.awt.Component.processMouseEvent(Component.java:5100)
        at java.awt.Component.processEvent(Component.java:4897)
        at java.awt.Container.processEvent(Container.java:1569)
        at java.awt.Component.dispatchEventImpl(Component.java:3615)
        at java.awt.Container.dispatchEventImpl(Container.java:1627)
        at java.awt.Component.dispatchEvent(Component.java:3477)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
        at java.awt.Container.dispatchEventImpl(Container.java:1613)
        at java.awt.Window.dispatchEventImpl(Window.java:1606)
        at java.awt.Component.dispatchEvent(Component.java:3477)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
[catch] at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)