title: Handling Firebase permission errors with AngularFire2
body: <p>I have a collection in Firebase that may occasionally be accessed by a user who doesn't have the right permissions. Right now when this happens, I'm getting a bunch of warnings and uncaught exceptions in the console and it seems to be impossible to handle them properly. I usually subscribe to an observable like this:</p>
  
  <pre><code>this.af.database.object('/someLocation/abc').subscribe(obj =&gt; {
      // logic
  });
  </code></pre>
  
  <p>Without loosening security rules, what is the best way to handle these unhandled exceptions?</p>