java.lang.NullPointerException
   at org.netbeans.modules.j2ee.jpa.refactoring.rename.RelationshipMappingRename.prepare(RelationshipMappingRename.java:117)
   at org.netbeans.modules.j2ee.jpa.refactoring.JPARefactoringPlugin.prepare(JPARefactoringPlugin.java:92)
   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.java.plugins.RenamePropertyRefactoringPlugin.prepare(RenamePropertyRefactoringPlugin.java:216)
   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$Prepare.run(ParametersPanel.java:1040)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)