java.lang.NullPointerException
   at org.netbeans.modules.refactoring.api.RefactoringSession.setWrappers(RefactoringSession.java:382)
   at org.netbeans.modules.refactoring.api.RefactoringSession.reallyUndoRefactoring(RefactoringSession.java:280)
   at org.netbeans.modules.refactoring.api.RefactoringSession.access$300(RefactoringSession.java:79)
   at org.netbeans.modules.refactoring.api.RefactoringSession$2.run(RefactoringSession.java:257)
   at org.netbeans.modules.refactoring.api.RefactoringSession$2.run(RefactoringSession.java:255)
   at org.netbeans.modules.editor.lib.BeforeSaveTasks.runWithOnSaveTasksDisabled(BeforeSaveTasks.java:93)
   at org.netbeans.editor.Utilities.runWithOnSaveTasksDisabled(Utilities.java:1616)
   at org.netbeans.modules.refactoring.api.RefactoringSession.undoRefactoring(RefactoringSession.java:255)
   at org.netbeans.modules.refactoring.spi.impl.UndoManager$SessionUndoItem.undo(UndoManager.java:464)
   at org.netbeans.modules.refactoring.spi.impl.UndoManager$1.run(UndoManager.java:226)
   at org.netbeans.modules.refactoring.spi.impl.UndoManager.undo(UndoManager.java:259)
   at org.netbeans.modules.refactoring.spi.impl.RefactoringUndoRedo.undo(RefactoringUndoRedo.java:86)
   at org.openide.actions.UndoRedoAction.actionPerformed(UndoRedoAction.java:224)
   at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
   at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
   at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
   at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
   at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
   at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:290)
   at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:289)
   at java.awt.Component.processMouseEvent(Component.java:6535)
   at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
   at java.awt.Component.processEvent(Component.java:6300)
   at java.awt.Container.processEvent(Container.java:2236)
   at java.awt.Component.dispatchEventImpl(Component.java:4891)
   at java.awt.Container.dispatchEventImpl(Container.java:2294)
   at java.awt.Component.dispatchEvent(Component.java:4713)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4888)
   at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4525)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4466)
   at java.awt.Container.dispatchEventImpl(Container.java:2280)
   at java.awt.Window.dispatchEventImpl(Window.java:2750)
   at java.awt.Component.dispatchEvent(Component.java:4713)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
   at java.awt.EventQueue.access$500(EventQueue.java:97)
   at java.awt.EventQueue$3.run(EventQueue.java:709)
   at java.awt.EventQueue$3.run(EventQueue.java:703)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
   at java.awt.EventQueue$4.run(EventQueue.java:731)
   at java.awt.EventQueue$4.run(EventQueue.java:729)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)