java.lang.NullPointerException
        at org.netbeans.modules.xml.dtd.grammar.ContentModel$MultiplicityGroup.eat(ContentModel.java:409)
        at org.netbeans.modules.xml.dtd.grammar.ContentModel$Sequence.eat(ContentModel.java:300)
        at org.netbeans.modules.xml.dtd.grammar.ContentModel.whatCanFollow(ContentModel.java:171)
        at org.netbeans.modules.xml.dtd.grammar.DTDGrammar.queryElements(DTDGrammar.java:217)
        at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.queryElements(XMLCompletionQuery.java:319)
        at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.query(XMLCompletionQuery.java:139)
        at org.netbeans.modules.xml.text.completion.XMLCompletionProvider.queryImpl(XMLCompletionProvider.java:134)
        at org.netbeans.modules.xml.text.completion.XMLCompletionProvider.access$000(XMLCompletionProvider.java:67)
        at org.netbeans.modules.xml.text.completion.XMLCompletionProvider$Query.doQuery(XMLCompletionProvider.java:105)
        at org.netbeans.modules.xml.text.completion.XMLCompletionProvider$Query.query(XMLCompletionProvider.java:117)
        at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:218)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:561)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:986)