title: angularjs collapse + ng-if doesn't work ng-show works
body: <p>I've got a button linked to a UI Bootstrap
  Collapse directive if I click on it
  the script show a form to reply a comment.
  when the form is showed I want to hide the button
  but I've got a strange behavior </p>
  
  <p>this doesn't work:</p>
  
  <pre><code>&lt;a data-ng-click="isCollapsed = !isCollapsed" data-ng-if="isCollapsed" class="btn btn-info btn-xs" title="reply comment"&gt;
      &lt;span class="glyphicon glyphicon-share-alt"&gt;&lt;/span&gt; Reply
  &lt;/a&gt;
  </code></pre>
  
  <p>this work:</p>
  
  <pre><code>&lt;a data-ng-click="isCollapsed = !isCollapsed" data-ng-show="isCollapsed" class="btn btn-info btn-xs" title="reply comment"&gt;
      &lt;span class="glyphicon glyphicon-share-alt"&gt;&lt;/span&gt; Reply
  &lt;/a&gt;
  </code></pre>
  
  <p>and I don't really know why !</p>
  
  <p>Can you enlighten me, please ?</p>