java.lang.IllegalStateException: Some of a set of deleted nodes are not present in the original ones.
See #15478; you may need to check that your Children.Keys keys are safely comparable.
i: 4
j: 0
This: org.openide.nodes.NodeMemberEvent[node=org.netbeans.modules.gsfret.navigation.ElementNode@13c92d5[Name=, displayName=div], add=false
  0 at 0 = org.netbeans.modules.gsfret.navigation.ElementNode@d0b397[Name=, displayName=a]
]
curr. snapshot: org.openide.nodes.EntrySupport$Default$DefaultSnapshot
[org.netbeans.modules.gsfret.navigation.ElementNode@154fd3a[Name=, displayName=div], org.netbeans.modules.gsfret.navigation.ElementNode@150f83a[Name=, displayName=div], org.netbeans.modules.gsfret.navigation.ElementNode@12758a1[Name=, displayName=div]]
prev. snapshot: java.util.Arrays$ArrayList
[org.netbeans.modules.gsfret.navigation.ElementNode@1554a0a[Name=, displayName=a], org.netbeans.modules.gsfret.navigation.ElementNode@154fd3a[Name=, displayName=div], org.netbeans.modules.gsfret.navigation.ElementNode@150f83a[N
        at org.openide.nodes.NodeMemberEvent.getDeltaIndices(NodeMemberEvent.java:176)
        at org.openide.explorer.view.VisualizerNode.childrenRemoved(VisualizerNode.java:373)
Caused: java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:0)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:450)
Caused: java.lang.reflect.UndeclaredThrowableException
        at $Proxy5.childrenRemoved(.java:0)
        at org.openide.nodes.Node.fireSubNodesChange(Node.java:1084)
        at org.openide.nodes.EntrySupport$Default.notifyRemove(EntrySupport.java:657)
        at org.openide.nodes.EntrySupport$Default.updateRemove(EntrySupport.java:380)
        at org.openide.nodes.EntrySupport$Default.setEntries(EntrySupport.java:335)
        at org.openide.nodes.Children$Keys$2.run(Children.java:1502)
        at org.openide.util.Mutex$1Exec.run(Mutex.java:1239)
        at org.openide.nodes.Children$ProjectManagerDeadlockDetector.execute(Children.java:1808)
        at org.openide.util.Mutex.postRequest(Mutex.java:1245)
        at org.openide.util.Mutex.postRequest(Mutex.java:1209)
        at org.openide.util.Mutex.postWriteRequest(Mutex.java:582)
        at org.openide.nodes.Children$Keys.applyKeys(Children.java:1511)
        at org.openide.nodes.Children$Keys.setKeys(Children.java:1455)
        at org.netbeans.modules.gsfret.navigation.ElementNode$ElementChildren.resetKeys(ElementNode.java:325)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:269)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ElementNode.updateRecursively(ElementNode.java:281)
        at org.netbeans.modules.gsfret.navigation.ClassMemberPanelUI$3.run(ClassMemberPanelUI.java:213)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)