title: Flutter `FirebaseDynamicLinks.onLink` calls `onSuccess` twice when the app is in background
body: <p>in pubspec.yaml:</p>
  
  <pre><code>firebase_dynamic_links: ^0.5.0+11
  </code></pre>
  
  <p>The code:</p>
  
  <pre><code>    FirebaseDynamicLinks.instance.onLink(
          onSuccess: (PendingDynamicLinkData dynamicLink) async {
            final Uri deepLink = dynamicLink?.link;
            if (deepLink != null) {
              onLinkReceived(deepLink);
            }
          },
          onError: onError);
    }
  </code></pre>
  
  <ol>
  <li>The app is launched and in background.</li>
  <li>User clicks the link.</li>
  </ol>
  
  <p>Actual result: <code>onSuccess</code> is being called twice for the link.</p>
  
  <p>Expected result: <code>onSuccess</code> is being called and being called once per link.</p>
  
  <p>What could be wrong?</p>