title: How to have a floating label on md-input-container when ng-model is null
body: <p>What I want to achieve is either this:</p>
  
  <p><img src="https://i.stack.imgur.com/7BdgK.png" alt="Option 1"></p>
  
  <p>Or this:</p>
  
  <p><img src="https://i.stack.imgur.com/vHvLo.jpg" alt="Option 2"></p>
  
  <p>Current Code:</p>
  
  <pre><code>&lt;md-input-container  ng-if="!ctl.module.activeDate" placeholder = "NotSetted"&gt;
      &lt;label&gt;Activation Date&lt;/label&gt;
      &lt;md-datepicker ng-model="" disabled&gt;&lt;/md-datepicker&gt;
  &lt;/md-input-container&gt;
  </code></pre>
  
  <p>This implementation is using Angular Material. I check with the ng-if if the <code>activeDate</code> is <code>null</code>, if it's not I have another <code>md-input-container</code> that gets the value, that is a "workaround" solution, the best way would be to have all of that logic in the same <code>md-input-container</code>.</p>