java.lang.AssertionError
        at org.netbeans.editor.ext.html.parser.SyntaxTree.makeTree(SyntaxTree.java:71)
        at org.netbeans.editor.ext.html.parser.SyntaxParserResult.getASTRoot(SyntaxParserResult.java:74)
        at org.netbeans.modules.html.editor.gsf.api.HtmlParserResult.root(HtmlParserResult.java:84)
        at org.netbeans.modules.html.editor.gsf.api.HtmlParserResult.findErrors(HtmlParserResult.java:126)
        at org.netbeans.modules.html.editor.gsf.api.HtmlParserResult.getDiagnostics(HtmlParserResult.java:114)
        at org.netbeans.modules.csl.core.TLIndexerFactory$TLIndexer.index(TLIndexerFactory.java:171)
        at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor.index(Indexable.java:194)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.visit(RepositoryUpdater.java:1332)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.visit(RepositoryUpdater.java:1346)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1315)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:129)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:113)
        at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:189)
        at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:99)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.indexEmbedding(RepositoryUpdater.java:1306)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.index(RepositoryUpdater.java:1220)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.scanSource(RepositoryUpdater.java:2129)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.scanSources(RepositoryUpdater.java:2046)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.getDone(RepositoryUpdater.java:1826)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doTheWork(RepositoryUpdater.java:1398)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task._run(RepositoryUpdater.java:2476)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task.run(RepositoryUpdater.java:2423)
        at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:581)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:619)