title: Awaiting with null coalescing operator thrown exception
body: <p>I'm encountering some strange behavior.</p>
  
  <p>When running this piece of code:</p>
  
  <pre><code>var foo = await actionContext.RequestContext?.Principal?.ToUserTokenAsync() ?? UserToken.UnidentifiedUser;
  </code></pre>
  
  <p><code>Principal</code> is <code>null</code> at runtime and I get a null reference exception.</p>
  
  <p>Why it's not just returning --> <code>UserToken.UnidentifiedUser</code>?</p>