javax.swing.text.BadLocationException: Modification not allowed
   at org.openide.text.CloneableEditorSupport$DocFilter.modificationNotAllowed(CloneableEditorSupport.java:2430)
   at org.openide.text.CloneableEditorSupport$DocFilter.checkModificationAllowed(CloneableEditorSupport.java:2424)
   at org.openide.text.CloneableEditorSupport$DocFilter.insertString(CloneableEditorSupport.java:2360)
   at org.netbeans.editor.BaseDocument.insertString(BaseDocument.java:749)
   at org.netbeans.modules.cnd.highlight.hints.MissingGuardBlock$AddGuardBlock.implement(MissingGuardBlock.java:236)
   at org.netbeans.modules.editor.hints.HintsUI$1.run(HintsUI.java:837)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)