java.net.MalformedURLException: no protocol: nullwww.w3.org/TR/css3-flexbox/index.html#align-content
   at java.net.URL.<init>(URL.java:593)
   at java.net.URL.<init>(URL.java:490)
   at java.net.URL.<init>(URL.java:439)
   at org.netbeans.modules.css.editor.module.main.StandardPropertiesHelpResolver.getHelp(StandardPropertiesHelpResolver.java:0)
   at org.netbeans.modules.css.editor.module.CssModuleSupport$7.getHelp(CssModuleSupport.java:0)
   at org.netbeans.modules.css.editor.csl.CssCompletion.document(CssCompletion.java:0)
   at org.netbeans.modules.csl.editor.completion.GsfCompletionDoc.<init>(GsfCompletionDoc.java:126)
   at org.netbeans.modules.csl.editor.completion.GsfCompletionDoc.create(GsfCompletionDoc.java:137)
   at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery.resolveDocumentation(GsfCompletionProvider.java:553)
   at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery.access$600(GsfCompletionProvider.java:250)
   at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery$1.run(GsfCompletionProvider.java:340)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:0)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:0)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:0)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:0)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:0)
   at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:0)
   at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:0)
   at org.netbeans.modules.parsing.nb.DataObjectEnvFactory.runPriorityIO(DataObjectEnvFactory.java:0)
   at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:0)
   at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:0)
   at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:0)
   at org.netbeans.modules.csl.editor.completion.GsfCompletionProvider$JavaCompletionQuery.query(GsfCompletionProvider.java:345)
   at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:0)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:0)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:0)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:0)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:0)