title: Property 'catch' does not exist on type 'PromiseLike<any>'
body: <p>I have the following code:</p>
  
  <pre><code>this.afDb.list('/demo').push({a: 'b'})
      .then(_ =&gt; console.log('works'))
      .catch(err =&gt; console.log('err: ', err));
  </code></pre>
  
  <p>I get the following error on 'catch':</p>
  
  <pre><code>[ts] Property 'catch' does not exist on type 'PromiseLike&lt;any&gt;'.
  </code></pre>
  
  <p>Seems like a AngularFire2 bug?</p>