title: Tree Panel 'nodeexpand' event in Extjs6.5 not working
body: <p>I am trying to create a TreePanel is something like a folder explorer. I am trying to find the event when I click the Node Expander (as the following screenshot) in my tree panel.</p>
  
  <p><a href="https://i.stack.imgur.com/dlicc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dlicc.png" alt=""></a></p>
  
  <p>Does anyone know what's the correct event?</p>
  
  <p>Here's the code for my view:</p>
  
  <pre><code>Ext.define('HDDTest.view.mod.searchDetails', {
      extend: 'Ext.Panel',
      xtype:'searchDetails',
      controller: 'home',
      requires: [
          'HDDTest.view.mod.PreviewPlugins.PreviewPlugin',
          'Ext.grid.*',
          'Ext.data.*',
          'Ext.util.*',
          'Ext.toolbar.Paging',
          'Ext.tip.QuickTipManager'
      ],
      items: [
          {
              xtype: 'treepanel',
              iconCls: 'icon-tree',
              title: 'Tree',
              collapsible: true,
              height: 300,
              padding:'0 20 0 0',
              rootVisible: false,
              id: 'treePanel',
              name:'treePanel',
              store: {
                  type: 'TreeBufferStore'
              },
              listeners: {
                  itemclick: 'onNodesSelected',
                  nodeexpand  : 'onNodesSelected2' //&lt;== It can not work
              },
  
              columns: [{
                  xtype: 'treecolumn', //this is so we know which column will show the tree
                  text: 'Representation',
                  width: 360,
                  sortable: true,
                  dataIndex: 'text',
                  locked: true
              }, {
                  text: 'Parents',
                  width: 430,
                  dataIndex: 'From',
                  sortable: true
              }, {
                  text: 'NCID',
                  width: 430,
                  dataIndex: 'ncid',
                  sortable: true
  
              }]
          }
      ]
  });
  </code></pre>
  
  <p>I get nothing. How can I do for this?</p>