Ext运行页面出错：'events'为空或不是对象，不知道什么地方出错了！

<body>
  <script type="text/javascript" language="javascript">
   function allFunction(){
     init();
     initTabPanel()
   }
   
   function init()
{
 new Ext.Viewport({
     layout:'border',
 items:[
    {region:'north',
       html:'n',title:'北',height:100,collapsible:true,
       split:true,minSize:50,maxSize:150},
    {region:'south',html:'s',title:'南',height:100,collapsible:true},
                                {region:'west',contentEl:"div_west",title:'西',width:200,collapsible:true},
    {region:'east',contentEl:"div_east",title:'东',width:200,collapsible:true},
    tabPanel
 ]
 });
        }
    
       var tabPanel;
       function initTabPanel()
        {
            tabPanel = new Ext.TabPanel({
                 region:"center",
                activeTab:1,
                enableTabScroll:true,
                items:[
                {
                   id:1,
                   title:"百度",
                   closable:true,
                   html:"<iframe src='http://www.baidu.com' width='100%' height='1000px'></iframe>" 
                },
                {
                   id:2,
                   title:"谷歌",
                   closable:true,
                   html:"<iframe src='http://www.google.com' width='100%' height='1000px'></iframe>" 
                }
                ]
            });
        }
     Ext.onReady(function(){allFunction();});
  </script>
   <div id="div_west"></div>
   <div id="div_east"></div>
</body>页面运行时报错：'events'为空或不是对象。不知道什么地方出错了！