java.lang.IllegalStateException: Not locker. lockThread=null
   at org.netbeans.lib.editor.util.PriorityMutex.unlock(PriorityMutex.java:122)
   at org.netbeans.modules.editor.lib2.view.DocumentView.unlock(DocumentView.java:272)
   at org.netbeans.modules.editor.lib2.view.DocumentView.runTransaction(DocumentView.java:215)
   at org.netbeans.modules.editor.lib2.view.DocumentView$1.run(DocumentView.java:226)
   at org.netbeans.editor.BaseDocument.render(BaseDocument.java:1335)
   at org.netbeans.modules.editor.lib2.view.DocumentView.runReadLockTransaction(DocumentView.java:223)
   at org.netbeans.modules.editor.lib2.view.DocumentViewOp.syncViewsRebuild(DocumentViewOp.java:293)
   at org.netbeans.modules.editor.lib2.view.ViewUpdates$RebuildViews.run(ViewUpdates.java:443)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1411)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1991)
Caused: org.openide.util.RequestProcessor$FastItem: task failed due to: java.lang.IllegalStateException: Not locker. lockThread=null