title: TbButtonColumn $data error
body: <p>I'm trying to use <code>$data-&gt;id</code> on <code>TbButtonColumn</code> but I'm getting error <code>"Trying to get property of non-object"</code>.
  The <code>TbGridView</code> is working properly!
  What I'm doing wrong?</p>
  
  <p>View.php:</p>
  
  <pre><code>&lt;?php  $this-&gt;widget('bootstrap.widgets.TbGridView',array(
      'type'=&gt;'striped bordered condensed',
      'id'=&gt;'profiles-grid',
      'dataProvider'=&gt;$dataProvider,
      'columns'=&gt;array(
          'id',
          array(
              'class'=&gt;'bootstrap.widgets.TbButtonColumn',
              'template'=&gt;'{create}',
              'buttons'=&gt;array
              (
                  'create' =&gt; array(
                      'label'=&gt;'Criar Evento',
                      'icon'=&gt;'plus',
                      'url'=&gt;'Yii::app()-&gt;controller-&gt;createUrl("events/create", array("id"=&gt;$data-&gt;id))', // Problem here on $data-&gt;id
                  ),
              ),
          ),
      ),
  )); ?&gt;
  </code></pre>