java.lang.AssertionError: element length must be positive!
   at org.netbeans.modules.html.editor.lib.plain.AbstractElement.<init>(AbstractElement.java:68)
   at org.netbeans.modules.html.editor.lib.plain.CommentElement.<init>(CommentElement.java:56)
   at org.netbeans.modules.html.editor.lib.api.elements.ElementsIterator.comment(ElementsIterator.java:121)
   at org.netbeans.modules.html.editor.lib.api.elements.ElementsIterator.handleEOF(ElementsIterator.java:681)
   at org.netbeans.modules.html.editor.lib.api.elements.ElementsIterator.processNextToken(ElementsIterator.java:363)
   at org.netbeans.modules.html.editor.lib.api.elements.ElementsIterator.findNextElement(ElementsIterator.java:346)
   at org.netbeans.modules.html.editor.lib.api.elements.ElementsIterator.hasNext(ElementsIterator.java:323)
   at org.netbeans.modules.html.editor.lib.api.SyntaxAnalyzerResult.getHtmlTagDefaultNamespace(SyntaxAnalyzerResult.java:472)
   at org.netbeans.modules.html.editor.lib.api.SyntaxAnalyzerResult.detectHtmlVersion(SyntaxAnalyzerResult.java:149)
   at org.netbeans.modules.html.editor.lib.api.SyntaxAnalyzerResult.getDetectedHtmlVersion(SyntaxAnalyzerResult.java:130)
   at org.netbeans.modules.html.editor.lib.api.SyntaxAnalyzerResult.getHtmlVersion(SyntaxAnalyzerResult.java:108)
   at org.netbeans.modules.html.editor.api.gsf.HtmlParserResult.getHtmlVersion(HtmlParserResult.java:117)
   at org.netbeans.modules.html.editor.api.gsf.HtmlParserResult.getValidationResults(HtmlParserResult.java:249)
   at org.netbeans.modules.html.editor.api.gsf.HtmlParserResult.getDiagnostics(HtmlParserResult.java:235)
   at org.netbeans.modules.html.editor.hints.HtmlRuleContext.<init>(HtmlRuleContext.java:68)
   at org.netbeans.modules.html.editor.hints.HtmlHintsProvider.computeErrors(HtmlHintsProvider.java:199)
   at org.netbeans.modules.html.editor.HtmlErrorFilter.filter(HtmlErrorFilter.java:96)
   at org.netbeans.modules.csl.core.ErrorFilterQuery.getFilteredErrors(ErrorFilterQuery.java:67)
   at org.netbeans.modules.csl.core.TLIndexerFactory$TLIndexer.index(TLIndexerFactory.java:248)
   at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor$3.run(Indexable.java:216)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater.runIndexer(RepositoryUpdater.java:258)
   at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor.index(Indexable.java:214)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$3.run(RepositoryUpdater.java:2743)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:583)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:150)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:134)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:200)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:197)
   at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:168)
   at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:360)
   at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:72)
   at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:197)
   at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:102)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.indexEmbedding(RepositoryUpdater.java:2699)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doIndex(RepositoryUpdater.java:2492)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.access$1500(RepositoryUpdater.java:2015)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:2304)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:2302)
   at org.netbeans.modules.parsing.impl.indexing.errors.TaskCache.refreshTransaction(TaskCache.java:541)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.index(RepositoryUpdater.java:2302)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.scanFiles(RepositoryUpdater.java:2793)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$FileListWork.getDone(RepositoryUpdater.java:3151)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doTheWork(RepositoryUpdater.java:2883)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task._run(RepositoryUpdater.java:5103)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task.access$4800(RepositoryUpdater.java:4796)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task$2$1.run(RepositoryUpdater.java:5040)
   at org.netbeans.modules.parsing.impl.RunWhenScanFinishedSupport.performScan(RunWhenScanFinishedSupport.java:97)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task$2.call(RepositoryUpdater.java:5036)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task$2.call(RepositoryUpdater.java:5032)
   at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:168)
   at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:360)
   at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:72)
   at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task.run(RepositoryUpdater.java:5032)
   at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
   at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
   at java.util.concurrent.FutureTask.run(FutureTask.java:166)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1452)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2032)