title: Angular + Firebase - Authentication error / Database Rules issue
body: <p>I'm new to Angular2 and Firebase. And this is the first time I've tried authentication.  After setting the Firebase database Rules to:</p>
  <pre><code>service cloud.firestore {
    match /databases/{database}/documents {
      match /{document=**} {
        allow read, write: if request.auth != null;
      }
    }
  }
  </code></pre>
  <p>i get this error in the browser and I don't get any data loading:
  <a href="https://i.stack.imgur.com/PbuKf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PbuKf.png" alt="enter image description here" /></a></p>
  <p>The error is gone and data loads OK if the database is totally open like this (but i understand this is not good!):</p>
  <pre><code>rules_version = '2';
  service cloud.firestore {
    match /databases/{database}/documents {
       match /{document=**} {
         allow read, write;
       }
     }
   }
  </code></pre>
  <p>Can anyone tell me what Im doing wrong here please?</p>