             }
             
             for achievement in achievements {
-                if let id = achievement.identifier {
-                    self.achievements[id] = achievement
-                }
+                self.achievements[achievement.identifier] = achievement
             }
             
             completion?()

    // MARK: Private functions
    
    @objc fileprivate func authenticationChanged() {
        if GKLocalPlayer.localPlayer().isAuthenticated && !authenticated {
            authenticated = true
        } else {
            authenticated = false

            
            for player in players {
                print("Found player: \(String(describing: player.alias))")
                self.playersDict[player.playerID] = player
            }
            
            self.matchStarted = true
