title: Game Center leaderboard error
body: <p>I'm trying to get some leaderboards into my game and I'm getting the follow error:</p>
  
  <pre><code>No visible @interface for 'MGLGameCenterManager' declares the selector 'callDelegateOnMainThread:withArg:error:'
  </code></pre>
  
  <p>And it's in here,</p>
  
  <pre><code>- (void) authenticateLocalUser
  {
  if([GKLocalPlayer localPlayer].authenticated)
  {
      return;
  }
  
  [[GKLocalPlayer localPlayer] authenticateWithCompletionHandler:^(NSError *error)
   {
       [self callDelegateOnMainThread: @selector(processGameCenterAuthentication:) withArg:
        NULL error: error];
   }];
  }
  </code></pre>
  
  <p>What's the problem?</p>