java.lang.IllegalStateException
   at org.netbeans.modules.xml.dtd.grammar.ContentModel.parseContentModel(ContentModel.java:92)
   at org.netbeans.modules.xml.dtd.grammar.ContentModel.parseContentModel(ContentModel.java:72)
   at org.netbeans.modules.xml.dtd.grammar.DTDGrammar.queryElements(DTDGrammar.java:216)
   at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.queryElements(XMLCompletionQuery.java:316)
   at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.query(XMLCompletionQuery.java:125)
   at org.netbeans.modules.xml.text.completion.XMLCompletionProvider$Query.query(XMLCompletionProvider.java:124)
   at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:223)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)
Caused: org.openide.util.RequestProcessor$FastItem: task failed due to: java.lang.IllegalStateException