java.lang.IllegalStateException: This must happen in the event thread!
        at org.openide.awt.Actions$Bridge.propertyChange(Actions.java:272)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:252)
        at org.openide.util.SharedClassObject.firePropertyChange(SharedClassObject.java:386)
        at org.openide.util.SharedClassObject.putProperty(SharedClassObject.java:276)
        at org.openide.util.actions.SystemAction.setEnabled(SystemAction.java:108)
        at org.openide.util.actions.NodeAction.setEnabled(NodeAction.java:145)
        at org.openide.util.actions.CookieAction$CookiesChangeListener.propertyChange(CookieAction.java:227)
        at org.openide.nodes.Node.fireOwnPropertyChange(Node.java:953)
        at org.openide.nodes.Node.fireCookieChange(Node.java:928)
        at org.openide.src.nodes.ElementNode.superFireCookieChange(ElementNode.java:250)
        at org.openide.src.nodes.ElementNode$ElementListener.propertyChange(ElementNode.java:408)
        at org.openide.util.WeakListener$PropertyChange.propertyChange(WeakListener.java:349)
        at org.netbeans.modules.java.model.ElementImpl.firePropertyChangeEvent(ElementImpl.java:331)
        at org.netbeans.modules.java.model.DefaultLangModel.firePropertyChange(DefaultLangModel.java:698)
        at org.netbeans.modules.java.parser.ParsingSupport.fireElementPropertyChange(ParsingSupport.java:295)
        at org.netbeans.modules.java.JavaParserGlue.refireCookieChange(JavaParserGlue.java:368)
        at org.netbeans.modules.java.JavaParserGlue$SiblingListener.dataObjectPropertyChange(JavaParserGlue.java:531)
        at org.netbeans.modules.java.JavaParserGlue$SiblingListener.propertyChange(JavaParserGlue.java:457)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:252)
        at org.openide.loaders.DataObject.firePropertyChange(DataObject.java:787)
        at org.openide.loaders.MultiDataObject.fireCookieChange(MultiDataObject.java:698)
        at org.openide.loaders.MultiDataObject$3.stateChanged(MultiDataObject.java:752)
        at org.openide.nodes.CookieSet.fireChangeEvent(CookieSet.java:148)
        at org.openide.nodes.CookieSet.remove(CookieSet.java:68)
        at org.openide.text.EditorSupport$EntryEnv.removeSaveCookie(EditorSupport.java:845)
        at org.openide.text.EditorSupport.modifySaveCookie(EditorSupport.java:450)
        at org.openide.text.EditorSupport.notifyUnmodified(EditorSupport.java:404)
        at org.openide.text.EditorSupport$Del.notifyUnmodified(EditorSupport.java:529)
        at org.openide.text.CloneableEditorSupport.saveDocument(CloneableEditorSupport.java:632)
        at org.openide.text.DataEditorSupport.saveDocument(DataEditorSupport.java:265)
        at org.openide.text.EditorSupport$Del.superSaveDocument(EditorSupport.java:694)
        at org.openide.text.EditorSupport.saveDocument(EditorSupport.java:224)
        at org.netbeans.modules.java.JavaEditor.saveDocument(JavaEditor.java:421)
        at org.netbeans.modules.java.JavaEditor.saveDocument(JavaEditor.java:403)
        at org.netbeans.modules.form.FormEditorSupport.saveDocument(FormEditorSupport.java:213)
        at org.openide.text.EditorSupport$EntryEnv.save(EditorSupport.java:816)
        at org.netbeans.core.NbTopManager.saveAll(NbTopManager.java:407)
        at org.netbeans.core.NbTopManager$NbLifecycleManager.saveAll(NbTopManager.java:524)
        at org.openide.compiler.CompilerExecutor$CERunnable.run(CompilerExecutor.java:146)
        at org.netbeans.core.execution.RunClassThread.run(RunClassThread.java:125)