java.lang.AssertionError: Null children for accurate span
   at org.netbeans.modules.editor.lib2.view.ViewBuilder.replaceRepaintViews(ViewBuilder.java:1244)
   at org.netbeans.modules.editor.lib2.view.ViewBuilder.createReplaceRepaintViews(ViewBuilder.java:686)
   at org.netbeans.modules.editor.lib2.view.ViewUpdates.updateViewsByModification(ViewUpdates.java:303)
   at org.netbeans.modules.editor.lib2.view.ViewUpdates.insertUpdate(ViewUpdates.java:239)
   at sun.reflect.GeneratedMethodAccessor107.invoke(GeneratedMethodAccessor107.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:601)
   at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:457)
   at $Proxy20.insertUpdate(.java:0)
   at org.netbeans.lib.editor.util.swing.PriorityDocumentListenerList.insertUpdate(PriorityDocumentListenerList.java:85)
   at javax.swing.text.AbstractDocument.fireInsertUpdate(AbstractDocument.java:202)
   at org.netbeans.editor.BaseDocument.fireInsertUpdate(BaseDocument.java:1570)
   at org.netbeans.editor.BaseDocument.handleInsertString(BaseDocument.java:818)
   at org.netbeans.editor.BaseDocument.insertString(BaseDocument.java:758)
   at org.netbeans.editor.BaseDocument.read(BaseDocument.java:1401)
   at org.netbeans.editor.BaseKit.read(BaseKit.java:708)
   at org.netbeans.modules.nbform.FormEditorSupport.loadFromStreamToKit(FormEditorSupport.java:1371)
   at org.openide.text.CloneableEditorSupport.loadDocument(CloneableEditorSupport.java:2121)
   at org.openide.text.CloneableEditorSupport.access$2900(CloneableEditorSupport.java:129)
   at org.openide.text.CloneableEditorSupport$Listener.run(CloneableEditorSupport.java:2959)
   at org.openide.text.CloneableEditorSupport$6$1Query.call(CloneableEditorSupport.java:1776)
   at org.openide.text.CloneableEditorSupport$6.run(CloneableEditorSupport.java:1787)
   at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:317)
   at org.openide.text.NbDocument.runAtomic(NbDocument.java:436)
   at org.openide.text.CloneableEditorSupport.reloadDocument(CloneableEditorSupport.java:1737)
   at org.netbeans.modules.nbform.FormEditorSupport.reloadDocument(FormEditorSupport.java:627)
   at org.openide.text.CloneableEditorSupport.checkReload(CloneableEditorSupport.java:2314)
   at org.openide.text.CloneableEditorSupport.access$2700(CloneableEditorSupport.java:129)
   at org.openide.text.CloneableEditorSupport$Listener$1.run(CloneableEditorSupport.java:2924)
   at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:317)
   at org.openide.text.NbDocument.runAtomic(NbDocument.java:436)
   at org.openide.text.CloneableEditorSupport$Listener$1.run(CloneableEditorSupport.java:2913)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705)
   at java.awt.EventQueue.access$000(EventQueue.java:101)
   at java.awt.EventQueue$3.run(EventQueue.java:666)
   at java.awt.EventQueue$3.run(EventQueue.java:664)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:675)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:158)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)