title: Uncaught InvalidValueError: setMap: not an instance of Map
body: <p>when i used the sencha touch2.2.1,i met a question.
  In the viewer:</p>
  
  <pre><code>items: [{
      id: 'mapCanvas',
      xtype:'map',
      useCurrentLocation: true,
  }]
  </code></pre>
  
  <p>In the controller:</p>
  
  <pre><code>var map= Ext.getCmp('mapCanvas');
  console.dir(map);
  var marker= new google.maps.Marker({
                  position: new google.maps.LatLng(25,118),
              });
  marker.setMap(map);
  </code></pre>
  
  <p>report the error:</p>
  
  <p>Uncaught InvalidValueError: setMap: not an instance of Map, and not an instance of StreetViewPanorama</p>
  
  <p>I can see the map,but i can't see the marker, and how to solve the problem?</p>