title: ng-repeat and select/optgroup not as expected
body: <p>I am having an issue with using ng-repeat and select.</p>
  
  <p>Here is my code, first of all</p>
  
  <pre><code>        &lt;select&gt;
              &lt;optgoup ng-repeat="(key, value) in Widget.ids" label="{{ value.label }}"&gt;
                  &lt;option ng-repeat="id in Widget.ids[key].ids"&gt;{{ id }}&lt;/option&gt;
              &lt;/optgroup&gt;
          &lt;/select&gt;
  </code></pre>
  
  <p>My data looks something like this</p>
  
  <pre><code>        [ 
          { label: "My Label", ids: [ "one id", "another id" ] },
          { label: "My Other Label", ids: [ "one id", "another id" ] }
          ]
  </code></pre>
  
  <p>However, this returns a completely empty <code>&lt;select&gt;</code>. 
  What's frustrating, is if I change my HTML to look like this:</p>
  
  <pre><code>            &lt;div ng-repeat="(key, value) in Widget.ids"&gt;{{ value.label }}
                  &lt;div ng-repeat="id in Widget.ids[key].ids"&gt;{{ id }}&lt;/div&gt;
              &lt;/div&gt;      
  </code></pre>
  
  <p>Then it lists..</p>
  
  <pre><code>My label
  one id
  another id
  My Other Label
  one id
  another id
  </code></pre>
  
  <p>In fact if I remove the <code>&lt;select&gt;</code> tag and leave the <code>optgroup</code> etc tags then it will actually generate the correct DOM elements. </p>
  
  <p>Also, I can't use simply use ng-model as I will be reserving that for a different model. (Widget.my.path.widget_id)</p>
  
  <p>What's going on here then?</p>