title: firebase displayName and photoURL are not nullable
body: <p>I am working on angular application using angularFire2. I am trying to update just the user displayName.</p>
  
  <p>documentation bellow states both displayName and photoURL should be nullable and that we should omit the part we dont want to update.
  <a href="https://firebase.google.com/docs/reference/js/firebase.User#updateProfile" rel="nofollow noreferrer">https://firebase.google.com/docs/reference/js/firebase.User#updateProfile</a></p>
  
  <p>When i try to run same code in the sample it gives error. Any idea? 
  <a href="https://i.stack.imgur.com/fVfh4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fVfh4.png" alt="enter image description here"></a></p>
  
  <p>Edit:</p>
  
  <p>User object is interface imported from firebase..so no angularfire</p>
  
  <pre><code>import { auth, User } from 'firebase/app';
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/RaMi0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RaMi0.png" alt="enter image description here"></a></p>