title: JavaScript / ExtJs : TreePanel / TreeLoader : how to handle load errors?
body: <p>Almost everything is in the title ;)</p>
  
  <p>When you create a TreePanel you can add a loader this way:</p>
  
  <pre><code>loader: new Ext.tree.TreeLoader({
    dataUrl: '../myurl.php'
  });
  </code></pre>
  
  <p>But how to handle load errors?</p>
  
  <p>For example if the user is not connected I want to display a Login box.</p>
  
  <p>I can't find an example showing how to handle loading errors with <code>TreeLoader</code> and/or <code>TreePanel</code>.</p>