java.lang.NullPointerException: Passed null to FileOwnerQuery.getOwner(FileObject)
	at org.netbeans.api.project.FileOwnerQuery.getOwner(FileOwnerQuery.java:59)
	at org.netbeans.modules.refactoring.CheckUtils.isElementInOpenProject(CheckUtils.java:276)
	at org.netbeans.modules.refactoring.plugins.SafeDeleteRefactoringPlugin.preCheck(SafeDeleteRefactoringPlugin.java:127)
	at org.netbeans.modules.refactoring.api.AbstractRefactoring.pluginsPreCheck(AbstractRefactoring.java:271)
	at org.netbeans.modules.refactoring.api.AbstractRefactoring.preCheck(AbstractRefactoring.java:125)
	at org.netbeans.modules.refactoring.spi.ui.ParametersPanel$9.run(ParametersPanel.java:441)
	at org.openide.util.Task.run(Task.java:207)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:469)
[catch] at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:870)