title: extjs 4Uncaught TypeError: Cannot read property 'items' of undefined
body: <p>i want load a chart with store and model by sample data.But when loading data get a error: Cannot read property 'items' of undefined
  i creating a store and model in conroller and set chart values:</p>
  
  <pre><code>var chart = Ext.create('Ext.chart.Chart', {
                      animate: true,
                      store: Ext.create('Ext.data.Store', {
                          model: Ext.create('Ext.data.Model', {
                                  fields: ['temperature', 'date']
                              }
                          ),
                          data: [
                              {temperature: 58, date: new Date(2011, 1, 1, 8)},
                              {temperature: 63, date: new Date(2011, 1, 1, 9)},
                              {temperature: 73, date: new Date(2011, 1, 1, 10)},
                              {temperature: 78, date: new Date(2011, 1, 1, 11)},
                              {temperature: 81, date: new Date(2011, 1, 1, 12)}
                          ]
                      }),
                      axes: [{
                          type: 'numeric',
                          position: 'left',
                          title: 'y',
                          minimum: 0
                      },
                          {
                              type: 'date',
                              position: 'bottom',
                              title: 'x',
                              minimum: 0
                          }],
                      series: [{
                          type: 'column',
                          axis: 'left',
                          highlight: true,
                          tips: {
                              trackMouse: true,
                              width: 140,
                              height: 28
                          }
                      },
                          {
                              label: {
                                  display: 'insideEnd',
                                  'text-anchor': 'middle',
                                  renderer: Ext.util.Format.numberRenderer('0'),
                                  orientation: 'vertical',
                                  color: '#333'
                              },
                          }
                      ],
                  });
  </code></pre>
  
  <p>and i want add this chart to panel</p>
  
  <pre><code>Ext.ComponentQuery.query('panel')[0].add(chart);
  </code></pre>