title: Extjs4 Ext.view.View selectionchange event trigger twise when select item
body: <p>I am using Ext.view.View for my data view. When I select one item 'selectionchange' event trigger twice. But without "multiSelect:true" it only trigger once. </p>
  
  <pre><code>Ext.define('myViewView', {
      extend: 'Ext.view.View',
      alias: 'widget.myViewView',
      store: myContentStore,
      cls: 'content-view-view',
      tpl: myContentViewTpl,
      multiSelect: true,
      trackOver: true,
      overItemCls: 'x-item-over',
      itemSelector: '.thumb-wrap',
      emptyText: emptyDataText,
      resizable: true,
      style: {
          overflow: 'auto'
      },
      listeners: {
          selectionchange: function(dv, selections) {
  
          }
      },
      prepareData: function(data) {
          Ext.apply(data, {
              sizeString: Ext.util.Format.fileSize(data.size),
              modifiedString: Ext.util.Format.date(data.modified, "m-d-Y:g-i-a"),
              fileFormatPath: createBreadCrumb(data.filePath, false)
          });
          return data;
      }
  
  });
  </code></pre>