java.lang.ClassCastException: org.openide.loaders.DefaultDataObject cannot be cast to org.openide.loaders.DataFolder
   at org.openide.loaders.DataObjectPool.deregister(DataObjectPool.java:860)
   at org.openide.loaders.DataObjectPool.access$900(DataObjectPool.java:60)
   at org.openide.loaders.DataObjectPool$Item.deregister(DataObjectPool.java:1000)
   at org.openide.loaders.DataObject.dispose(DataObject.java:230)
   at org.openide.loaders.DataObject.markInvalid0(DataObject.java:273)
   at org.openide.loaders.MultiDataObject.notifyFileDeleted(MultiDataObject.java:1442)
   at org.openide.loaders.DataObjectPool$FSListener.fileDeleted(DataObjectPool.java:652)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEventImpl(FCLSupport.java:181)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapperMulti.dispatchAllEventsSync(FCLSupport.java:248)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEvent(FCLSupport.java:137)
   at org.openide.filesystems.FCLSupport.dispatchEvent(FCLSupport.java:112)
   at org.openide.filesystems.FileObject$ED.dispatch(FileObject.java:1435)
   at org.openide.filesystems.EventControl.invokeDispatchers(EventControl.java:213)
   at org.openide.filesystems.EventControl.exitAtomicAction(EventControl.java:188)
   at org.openide.filesystems.EventControl.finishAtomicAction(EventControl.java:116)
   at org.openide.filesystems.FileSystem.finishAtomicAction(FileSystem.java:545)
   at org.openide.filesystems.MultiFileObject.updateAll(MultiFileObject.java:279)
   at org.openide.filesystems.MultiFileObject.fileDeleted(MultiFileObject.java:1517)
   at sun.reflect.GeneratedMethodAccessor14.invoke(GeneratedMethodAccessor14.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:487)
   at org.openide.filesystems.$Proxy0.fileDeleted(.java:0)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEventImpl(FCLSupport.java:181)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapperSingle.dispatchAllEventsSync(FCLSupport.java:224)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEvent(FCLSupport.java:137)
   at org.openide.filesystems.FCLSupport.dispatchEvent(FCLSupport.java:105)
   at org.openide.filesystems.FileObject$ED.dispatch(FileObject.java:1398)
   at org.openide.filesystems.EventControl.invokeDispatchers(EventControl.java:213)
   at org.openide.filesystems.EventControl.exitAtomicAction(EventControl.java:188)
   at org.openide.filesystems.EventControl.finishAtomicAction(EventControl.java:116)
   at org.openide.filesystems.FileSystem.finishAtomicAction(FileSystem.java:545)
   at org.openide.filesystems.MultiFileObject.updateAllAfterSetDelegates(MultiFileObject.java:316)
   at org.openide.filesystems.MultiFileSystem.setDelegates(MultiFileSystem.java:199)
   at org.netbeans.modules.apisupport.project.api.LayerHandle$DualLayers.configure(LayerHandle.java:289)
   at org.netbeans.modules.apisupport.project.api.LayerHandle$DualLayers.fileDeleted(LayerHandle.java:298)
   at org.openide.filesystems.FileChangeImpl.fileDeleted(FileChangeImpl.java:149)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEventImpl(FCLSupport.java:181)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapperSingle.dispatchAllEventsSync(FCLSupport.java:224)
   at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEvent(FCLSupport.java:137)
   at org.openide.filesystems.FCLSupport$1.run(FCLSupport.java:261)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)