title: Extjs 4.1 disable panel preview when collapsed
body: <p>Let's suppose that we have the following code:</p>
  
  <pre><code>Ext.create ( 'Ext.container.Viewport', {
      layout : 'border',
      items  : [{
          region : 'west',
          xtype  : 'panel',
          collapsible : true,
          id     : 'panel1_id',
          width  : '45%'
      }, {
          region    : 'center',
          xtype     : 'panel',
          id        : 'panel2_id',
          width     : '55%'
      }]
  });
  </code></pre>
  
  <p>As we can see, the first panel is collapsible. My question is: 
  is it possible to disable the panel's preview (when we click on the collapsed panel's header) when collapsed?</p>