java.lang.NullPointerException
   at org.netbeans.modules.groovy.refactoring.rename.RenameRefactoringPlugin.isAlreadyInResult(RenameRefactoringPlugin.java:120)
   at org.netbeans.modules.groovy.refactoring.rename.RenameRefactoringPlugin.addModificationToResult(RenameRefactoringPlugin.java:101)
   at org.netbeans.modules.groovy.refactoring.rename.RenameRefactoringPlugin.collectModifications(RenameRefactoringPlugin.java:95)
   at org.netbeans.modules.groovy.refactoring.rename.RenameRefactoringPlugin.refactorResults(RenameRefactoringPlugin.java:81)
   at org.netbeans.modules.groovy.refactoring.findusages.FindUsagesPlugin.prepare(FindUsagesPlugin.java:85)
   at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare2(AbstractRefactoring.java:437)
   at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare(AbstractRefactoring.java:421)
   at org.netbeans.modules.refactoring.api.AbstractRefactoring.prepare(AbstractRefactoring.java:232)
   at org.netbeans.modules.refactoring.spi.impl.ParametersPanel$Prepare.run(ParametersPanel.java:1020)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1454)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2043)