java.lang.NullPointerException: The sources[0] parameter cannot be null
   at org.openide.util.Parameters.notNull(Parameters.java:89)
   at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:105)
   at org.netbeans.modules.web.inspect.ui.CssStylesPanelProviderImpl$WebCssStylesPanelListener$1.run(CssStylesPanelProviderImpl.java:500)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)