java.lang.IllegalStateException: This must happen in the event thread!
        at org.openide.awt.Actions$Bridge.propertyChange(Actions.java:272)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:252)
        at org.openide.util.SharedClassObject.firePropertyChange(SharedClassObject.java:386)
        at org.openide.util.SharedClassObject.putProperty(SharedClassObject.java:276)
        at org.openide.util.actions.SystemAction.setEnabled(SystemAction.java:108)
        at org.openide.util.actions.CallbackSystemAction.updateEnabled(CallbackSystemAction.java:140)
        at org.openide.util.actions.CallbackSystemAction.setActionPerformer(CallbackSystemAction.java:118)
        at org.netbeans.modules.properties.PropertiesOpen$3.run(PropertiesOpen.java:824)
        at org.openide.util.Task.run(Task.java:136)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:330)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:677)