java.lang.NullPointerException
Caused: java.net.MalformedURLException
   at java.net.URL.<init>(URL.java:627)
   at java.net.URL.<init>(URL.java:490)
   at java.net.URL.<init>(URL.java:439)
   at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:620)
   at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(XMLVersionDetector.java:148)
   at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:805)
   at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:770)
   at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
   at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
   at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
   at org.jdom.input.SAXBuilder.build(SAXBuilder.java:453)
   at org.jdom.input.SAXBuilder.build(SAXBuilder.java:770)
   at org.netbeans.modules.maven.grammar.spi.AbstractSchemaBasedGrammar.<init>(AbstractSchemaBasedGrammar.java:69)
   at org.netbeans.modules.maven.grammar.MavenProjectGrammar.<init>(MavenProjectGrammar.java:101)
   at org.netbeans.modules.maven.grammar.DefaultGrammarFactory.isSupported(DefaultGrammarFactory.java:56)
   at org.netbeans.modules.maven.grammar.MavenQueryProvider.getGrammar(MavenQueryProvider.java:76)
   at org.netbeans.modules.xml.api.model.GrammarQueryManager$DefaultQueryManager.getGrammar(GrammarQueryManager.java:126)
   at org.netbeans.modules.xml.text.completion.GrammarManager.loadGrammar(GrammarManager.java:290)
   at org.netbeans.modules.xml.text.completion.GrammarManager.getGrammar(GrammarManager.java:107)
   at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.getPerformer(XMLCompletionQuery.java:275)
   at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.queryValues(XMLCompletionQuery.java:309)
   at org.netbeans.modules.xml.text.completion.XMLCompletionQuery.query(XMLCompletionQuery.java:100)
   at org.netbeans.modules.xml.text.completion.XMLCompletionProvider$Query.query(XMLCompletionProvider.java:199)
   at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:198)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1418)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:45)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:278)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)