title: Get selected row column value extjs grid
body: <p>I have a users grid. To delete one, select your row and click a button "delete".
  But, this not work.
  My code is:</p>
  
  <pre><code>var row = userGrid.getSelectionModel().getSelection();
  console.log(row.get('dni'))
  </code></pre>
  
  <p>Firefox says:</p>
  
  <blockquote>
    <p>TypeError: row.get is not a function</p>
  </blockquote>
  
  <p>Any idea ?.</p>