title: xtype: combo is not firing expand event
body: <p>I am working on <code>EXTJS 3.4</code> version and facing an issue with <code>xtype: combo</code>.</p>
  
  <p>For some records it is going to expand event for some not.</p>
  
  <p><strong>My code is like below:</strong></p>
  
  <pre><code>{
      xtype: 'combo',
      labelWidth: 0,
      store: this.comboBoxStore,
      mode: 'local',
      triggerAction: 'all',
      displayField: 'asupDate',
      minListWidth: 500,
      valueField: 'asupId',
      itemSelector: 'div.search-item',
      forceSelection: true,
      editable: false,
      width: 180,
      id: 'combo' + '-' + this.ptype + '-' + this.asupRecord.get('sysRefId'),
      listeners: {
          expand: function () {
              //stop special keys operations... like j, k and 1,2,3,4.
              this.getEl().addListener('keydown', me.onKeyDownFunction);
              //Call loadAsupRange to load/populate asupRange dropdown.
              var cdvMainPanelObj = Ext.ComponentMgr.get('cdvMainPanel');
  
              if (!Ext.isDefined(me.asupRecord)) {
                  var seriallNo = me.systemRecord.get('sn');
                  var systemNo = me.systemRecord.get('sysId');
              } else {
                  var seriallNo = me.asupRecord.get('sysSerialNo');
                  var systemNo = me.asupRecord.get('sysId');
              }
              cdvMainPanelObj.loadAsupRange(this, systemNo, seriallNo, me.ptype);
          },
          render: function () {
              Ext.QuickTips.register({
                  target: this.id,
                  text: utp_toolTips.cdv_dropdown_asupRangeCombo
              });
          }
      }
  }
  </code></pre>
  
  <p>Please let me know what I did wrong.</p>