java.lang.AssertionError
        at org.netbeans.modules.javafx.refactoring.impl.RenameRefactoringElement.init(RenameRefactoringElement.java:276)
        at org.netbeans.modules.javafx.refactoring.impl.RenameRefactoringElement.<init>(RenameRefactoringElement.java:100)
        at org.netbeans.modules.javafx.refactoring.impl.RenameRefactoringElement.create(RenameRefactoringElement.java:88)
        at org.netbeans.modules.javafx.refactoring.impl.plugins.RenameRefactoringPlugin.prepare(RenameRefactoringPlugin.java:239)
        at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare2(AbstractRefactoring.java:419)
        at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPrepare(AbstractRefactoring.java:403)
        at org.netbeans.modules.refactoring.api.AbstractRefactoring.prepare(AbstractRefactoring.java:214)
        at org.netbeans.modules.refactoring.spi.impl.ParametersPanel$Prepare.run(ParametersPanel.java:803)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:602)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1084)