Invalid help archives

If the Help archive contains invalid content such as:

• An invalid xml database file

Then the associated model will be declared as invalid (see ArticlesModel.isValid()).

In that case the viewer will stil open but will show no articles. For example:

   // get an invalid zip file as an URL
   URL url = < this is a very bad zip file >

   try {
     // create the Help factory
     JavaHelpFactory factory = new JavaHelpFactory(url);
     factory.create();
      
     // create the viewer component
     JFXHelpContentViewer viewer = new JFXHelpContentViewer();
     factory.install(viewer);
      
     Node pane = viewer.getComponent();    
     // do whatever you want with the Node 
   } catch (IOException | SAXException ex) {
     ex.printStackTrace();
   }

The result will be: