title: Sencha Touch: List detail .setActiveItem undefined
body: <p>Am putting together and app and attempting to get a list with a detail panel working. I have based it on the Sencha list video, but keep getting an error "TypeError: Result of expression 'abc.artistList.setActiveItem' [undefined] is not a function." when I try to click on an item and reveal the detail panel. The full code is below:</p>
  
  <pre><code>Ext.ns('abc', 'abc.panel', 'abc.store');
  
  // Models _____________________________________________________________________
  Ext.regModel('Artists', {
      fields: ['firstName', 'lastName']
  });
  
  
  // Stores _____________________________________________________________________
  abc.store.Artists = new Ext.data.Store({
      model: 'Artists',
      proxy: {
          type: 'ajax',
          url: 'http://localhost:8888/abc/stores/artists.json',
          reader: {
              type: 'json',
               root: 'artists'
          }
      },
      sorters: 'lastName',
      getGroupString : function(record) {
          return record.get('lastName')[0];
      },
      autoLoad: true
  });
  
  abc.artistDetail = new Ext.Panel({
              id: 'detailpanel',
              tpl: 'Hello, {firstName}!',
              dockedItems: [
                  {
                      xtype: 'toolbar',
                      items: [{
                          text: 'back',
                          ui: 'back',
                          handler: function() {
                              abc.panel.Artists.setActiveItem('artistList', {type:'slide', direction:'right'});
                          }
                      }]
                  }
              ]
          });
  
  abc.artistList = new Ext.List({
      title: 'Artists',
      store: abc.store.Artists,
      fullscreen: true,
      id: 'artistList',
      itemTpl: '&lt;div class="contact"&gt;{firstName} {lastName}&lt;/div&gt;',
      grouped: true,
      onItemDisclosure: function(record, btn, index) {
          abc.artistDetail.update(record.data);
          abc.panel.Artists.setActiveItem('detailpanel');
      }
  });
  
  abc.panel.Artists = Ext.extend(Ext.Panel, {
      id: 'artists',
      title: 'Artists',
      layout: 'card',
      fullscreen: true,
      cardSwitchAnimation: 'slide',
      iconCls: 'artists',
      items: [abc.artistList, abc.artistDetail],
  });
  
  abcPrimavera = new Ext.Application({
      name: "abcApp",
  
      onReady: function () {
          var app = new Ext.TabPanel({
              fullscreen: true,
              animation: false,
              tabBar: {
                  dock: 'bottom',
                  layout: {
                      pack: 'center'
                  }
              },
              items: [
              new abc.panel.Artists()]
          });
          }
  });
  </code></pre>
  
  <p>Any help would be brilliant.</p>
  
  <p>Thanks</p>