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: 1
j: 0
This: org.openide.nodes.NodeMemberEvent[node=org.netbeans.modules.csl.navigation.ElementNode@83e83a[Name=, displayName=h1], add=false
  0 at 0 = org.netbeans.modules.csl.navigation.ElementNode@776016[Name=, displayName=img]
]
curr. snapshot: org.openide.nodes.EntrySupport$Default$DefaultSnapshot
[]
prev. snapshot: java.util.Arrays$ArrayList
[org.netbeans.modules.csl.navigation.ElementNode@b81a8d[Name=, displayName=img]]
Current state:
[org.netbeans.modules.csl.navigation.ElementNode@b81a8d[Name=, displayName=img]]
Delta:
[org.netbeans.modules.csl.navigation.ElementNode@776016[Name=, displayName=img]]
        at org.openide.nodes.NodeMemberEvent.getDeltaIndices(NodeMemberEvent.java:176)
        at org.openide.explorer.view.VisualizerNode.childrenRemoved(VisualizerNode.java:371)
Caused: java.lang.reflect.InvocationTargetException
        at sun.reflect.GeneratedMethodAccessor79.invoke(GeneratedMethodAccessor79.java:0)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:451)
Caused: java.lang.reflect.UndeclaredThrowableException
        at $Proxy5.childrenRemoved(.java:0)
        at org.openide.nodes.Node.fireSubNodesChange(Node.java:1095)
        at org.openide.nodes.EntrySupport$Default.notifyRemove(EntrySupport.java:647)
        at org.openide.nodes.EntrySupport$Default.updateRemove(EntrySupport.java:379)
        at org.openide.nodes.EntrySupport$Default.setEntries(EntrySupport.java:333)
        at org.openide.nodes.Children$Keys$2.run(Children.java:1503)
        at org.openide.util.Mutex$1Exec.run(Mutex.java:1239)
        at org.openide.nodes.Children$ProjectManagerDeadlockDetector.execute(Children.java:1810)
        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$Keys.applyKeys(Children.java:1512)
        at org.openide.nodes.Children$Keys.setKeys(Children.java:1456)
        at org.netbeans.modules.csl.navigation.ElementNode$ElementChildren.resetKeys(ElementNode.java:319)
        at org.netbeans.modules.csl.navigation.ElementNode.updateRecursively(ElementNode.java:265)
        at org.netbeans.modules.csl.navigation.ElementNode.updateRecursively(ElementNode.java:277)
        at org.netbeans.modules.csl.navigation.ClassMemberPanelUI$3.run(ClassMemberPanelUI.java:210)
        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)