title: Invalidate form if disabled select option is chosen
body: <p>Is there a way to invalidate a form if <code>value="0"</code> in my select tag is chosen? The reason I did this is to have a default select option show up before a user see's anything.</p>
  
  <p>But even if a user doesn't choose anything, the form is valid.</p>
  
  <pre><code>&lt;form name="add_task_frm" ng-submit="!add_task_frm.$valid || functiontoUse()" novalidate&gt;
  
      &lt;input type="text" ng-model="name" required /&gt;
  
      &lt;select ng-model="action" required&gt;
          &lt;option value="0" selected disabled&gt;Choose an Action&lt;/option&gt;
          &lt;option value="description"&gt;See Description&lt;/option&gt;
          &lt;option value="view"&gt;View&lt;/option&gt;
      &lt;/select&gt;
  
      &lt;button type="submit"&gt;Submit&lt;/button&gt;
  
  &lt;/form&gt;
  </code></pre>