java.lang.AssertionError
        at org.openide.text.CloneableEditorSupport.getOpenedPanes(CloneableEditorSupport.java:868)
        at org.netbeans.modules.cnd.modelutil.CsmUtilities.getCsmFile(CsmUtilities.java:213)
        at org.netbeans.modules.cnd.highlight.HighlightProvider.checkClosed(HighlightProvider.java:217)
        at org.netbeans.modules.cnd.highlight.HighlightProvider.checkClosed(HighlightProvider.java:210)
        at org.netbeans.modules.cnd.highlight.HighlightProvider.access$100(HighlightProvider.java:56)
        at org.netbeans.modules.cnd.highlight.HighlightProvider$2.run(HighlightProvider.java:185)
        at org.netbeans.modules.cnd.modelimpl.csm.core.CodeModelRequestProcessor$1.run(CodeModelRequestProcessor.java:57)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:539)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:964)