java.lang.IllegalStateException
   at org.netbeans.api.editor.fold.Fold.extractToChildren(Fold.java:354)
   at org.netbeans.api.editor.fold.FoldHierarchy$ApiPackageAccessorImpl.foldExtractToChildren(FoldHierarchy.java:394)
   at org.netbeans.modules.editor.fold.FoldHierarchyTransactionImpl.addFold(FoldHierarchyTransactionImpl.java:956)
   at org.netbeans.modules.editor.fold.FoldHierarchyTransactionImpl.addFold(FoldHierarchyTransactionImpl.java:647)
   at org.netbeans.modules.editor.fold.FoldHierarchyTransactionImpl.commit(FoldHierarchyTransactionImpl.java:238)
   at org.netbeans.modules.editor.fold.FoldOperationImpl$Refresher.run(FoldOperationImpl.java:772)
   at org.netbeans.modules.editor.fold.FoldOperationImpl.update(FoldOperationImpl.java:494)
   at org.netbeans.spi.editor.fold.FoldOperation.update(FoldOperation.java:406)
   at org.netbeans.modules.csl.editor.fold.GsfFoldManager$CommitFolds.run(GsfFoldManager.java:685)
   at org.netbeans.editor.BaseDocument.render(BaseDocument.java:1391)
   at org.netbeans.modules.csl.editor.fold.GsfFoldManager$CommitFolds.run(GsfFoldManager.java:662)
   at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.run(GsfFoldManager.java:389)
   at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.run(GsfFoldManager.java:268)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callParserResultTask(TaskProcessor.java:568)
   at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:744)
   at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
   at java.util.concurrent.FutureTask.run(FutureTask.java:266)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)