title: How to hide/delete underline input Angular Material?
body: <p>I have input element in Angular Material:</p>
  
  <pre><code>&lt;md-input-container&gt;
  &lt;input type="text" mdInput placeholder=""&gt;
  &lt;/md-input-container&gt;
  </code></pre>
  
  <p>When input has focus it displays underline. How to hide or remove that?</p>
  
  <p>Seem I need to set <code>null</code> for <code>underlineRef</code>?</p>