java.lang.IllegalArgumentException: Task: org.netbeans.modules.java.editor.fold.JavaElementFoldManager$JavaElementFoldTask@1273129 is already scheduled
   at org.netbeans.modules.java.source.JavaSourceAccessor.addPhaseCompletionTask(JavaSourceAccessor.java:190)
   at org.netbeans.api.java.source.JavaSourceTaskFactory$3.addPhaseCompletionTask(JavaSourceTaskFactory.java:234)
   at org.netbeans.api.java.source.JavaSourceTaskFactory.stateChangedImpl(JavaSourceTaskFactory.java:187)
   at org.netbeans.api.java.source.JavaSourceTaskFactory.access$000(JavaSourceTaskFactory.java:81)
   at org.netbeans.api.java.source.JavaSourceTaskFactory$1.run(JavaSourceTaskFactory.java:142)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1418)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1960)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.IllegalArgumentException: Task: org.netbeans.modules.java.editor.fold.JavaElementFoldManager$JavaElementFoldTask@1273129 is already scheduled
   at org.openide.util.RequestProcessor.post(RequestProcessor.java:421)
   at org.netbeans.api.java.source.JavaSourceTaskFactory.fileObjectsChanged(JavaSourceTaskFactory.java:140)
   at org.netbeans.api.java.source.support.EditorAwareJavaSourceTaskFactory.access$100(EditorAwareJavaSourceTaskFactory.java:60)
   at org.netbeans.api.java.source.support.EditorAwareJavaSourceTaskFactory$ChangeListenerImpl.stateChanged(EditorAwareJavaSourceTaskFactory.java:96)
   at org.netbeans.api.java.source.support.OpenedEditors.fireChangeEvent(OpenedEditors.java:119)
   at org.netbeans.api.java.source.support.OpenedEditors.stateChanged(OpenedEditors.java:175)
   at org.netbeans.api.java.source.support.OpenedEditors$1.propertyChange(OpenedEditors.java:89)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
   at org.netbeans.api.editor.EditorRegistry.fireEvents(EditorRegistry.java:514)
   at org.netbeans.api.editor.EditorRegistry$AncestorL$1.actionPerformed(EditorRegistry.java:705)
   at javax.swing.Timer.fireActionPerformed(Timer.java:271)
   at javax.swing.Timer$DoPostEvent.run(Timer.java:201)
   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:138)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)