title: Scrollbar in extjs tree panel does not work
body: <p>Sometimes it happens that the scrollbar of my tree panel does not work anymore. While it's still possible to move the scrollbar, the tree doesn't move at all anymore. That happens to me in Firefox and in Chrome as well. </p>
  
  <p>Here is the source of my tree panel:</p>
  
  <p><pre><code></p>
  
  <p>var treeStore = Ext.create('Ext.data.TreeStore', {
      proxy: {
          type: 'ajax',
          url: '../tree.pl'
      }
  });</p>
  
  <p>var tree = Ext.create('Ext.tree.Panel', {
      store: treeStore,
      renderTo: 'tree',
      title: 'Tree',
      width: 400,
      height: 450,
      rootVisible:false,
      dockedItems: [{
          xtype: 'toolbar',
          dock: 'bottom',
          items: [
          {
              xtype: 'tbspacer',
              width: 340
          },
          {
              text: 'Search',
              handler: function(){
                          names = [];
                          Ext.Array.each(tree.getView().getChecked(), function(rec){
                              names.push(rec.get('text'));
                          });</p>
  
  <pre>                    resultStore.load({
                          params:{
                              search_type: 'tree',
                              tree_nodes: names.join('II'),
                          }
                      });
                  }
      }
      ]
  }]
  </code></pre>
  
  <p>});</p>
  
  <p></pre></p>