java.lang.IllegalArgumentException: Called DataObject.find on null
        at org.openide.loaders.DataObject.find(DataObject.java:477)
        at org.netbeans.modules.xml.validation.ui.ValidationOutputWindow.getStyledDocument(ValidationOutputWindow.java:211)
        at org.netbeans.modules.xml.validation.ui.ValidationOutputWindow.getLineNumber(ValidationOutputWindow.java:232)
        at org.netbeans.modules.xml.validation.ui.ValidationOutputWindow.showMessage(ValidationOutputWindow.java:156)
        at org.netbeans.modules.xml.validation.ui.ValidationOutputWindow.showError(ValidationOutputWindow.java:141)
        at org.netbeans.modules.xml.validation.ui.ValidationOutputWindow.displayValidationInformation(ValidationOutputWindow.java:99)
        at org.netbeans.modules.xml.validation.ValidationOutputWindowController.printGuidanceInformation(ValidationOutputWindowController.java:96)
        at org.netbeans.modules.xml.validation.ValidationOutputWindowController.validate(ValidationOutputWindowController.java:87)
        at org.netbeans.modules.xml.validation.ValidateXMLCookieImpl.validateXML(ValidateXMLCookieImpl.java:68)
        at org.netbeans.modules.xml.tools.actions.ValidateAction$RunAction.run(ValidateAction.java:123)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:572)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:997)