java.lang.IllegalStateException: The data object MultiFileObject@1f4cba[Templates/Project/Samples/ApiSupport] is invalid; you may not call getNodeDelegate on it any more; see #17020 and please fix your code
        at org.openide.loaders.DataObject.getNodeDelegate(DataObject.java:270)
        at org.netbeans.modules.project.ui.TemplatesPanel$CategoriesChildren.createNodes(TemplatesPanel.java:220)
        at org.netbeans.modules.project.ui.TemplatesPanel$CategoriesChildren.createNodes(TemplatesPanel.java:192)
        at org.openide.nodes.Children$Keys$KE.nodes(Children.java:1517)
        at org.openide.nodes.ChildrenArray.nodesFor(ChildrenArray.java:168)
        at org.openide.nodes.EntrySupport$Default$Info.nodes(EntrySupport.java:935)
        at org.openide.nodes.EntrySupport$Default.justComputeNodes(EntrySupport.java:234)
        at org.openide.nodes.ChildrenArray.nodes(ChildrenArray.java:101)
        at org.openide.nodes.EntrySupport$Default.getNodes(EntrySupport.java:155)
        at org.openide.nodes.EntrySupport$Default.createSnapshot(EntrySupport.java:137)
        at org.openide.nodes.NodeEvent.<init>(NodeEvent.java:59)
        at org.openide.nodes.Node.fireNodeDestroyed(Node.java:1110)
        at org.openide.nodes.Children$Keys.destroyNodes(Children.java:1467)
        at org.openide.nodes.EntrySupport$Default.notifyRemove(EntrySupport.java:665)
        at org.openide.nodes.EntrySupport$Default.updateRemove(EntrySupport.java:375)
        at org.openide.nodes.EntrySupport$Default.setEntries(EntrySupport.java:324)
        at org.openide.nodes.Children$Keys$2.run(Children.java:1411)
        at org.openide.util.Mutex.postRequest(Mutex.java:1262)
        at org.openide.util.Mutex.postWriteRequest(Mutex.java:582)
        at org.openide.nodes.Children$Keys.applyKeys(Children.java:1420)
        at org.openide.nodes.Children$Keys.setKeys(Children.java:1401)
        at org.netbeans.modules.project.ui.TemplatesPanel$CategoriesChildren.removeNotify(TemplatesPanel.java:205)
        at org.openide.nodes.EntrySupport$Default.finalizedChildrenArray(EntrySupport.java:890)
        at org.openide.nodes.ChildrenArray.finalize(ChildrenArray.java:84)
        at java.lang.ref.Finalizer.invokeFinalizeMethod(Finalizer.java:0)
        at java.lang.ref.Finalizer.runFinalizer(Finalizer.java:83)
        at java.lang.ref.Finalizer.access$100(Finalizer.java:14)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:160)