Null Value for Facebook ID when trying to Login to Windows Phone 8.1 App

I'm trying to integrate Facebook Login with my app. I've managed to log in, get the Profile Name, but not the Profile Picture. Upon inspection I realized it's due to null value in facebookID. How to fix this?

private void LoadUserInfo()
        {
            var UISyncContext = TaskScheduler.FromCurrentSynchronizationContext();
            FBSession fbSession = FBSession.Instance;
            var fb = new FacebookClient(fbSession.Token.AccessToken);

            fb.GetCompleted += (o, e) =>
            {
                if (e.Error != null)
                {
                    Task.Factory.StartNew(() =>
                    {
                        Debug.WriteLine(e.Error.Message);
                    }, new System.Threading.CancellationToken(), TaskCreationOptions.PreferFairness, UISyncContext);
                    return;
                }

                var result = (IDictionary<string, object>)e.GetResultData();

                Task.Factory.StartNew(() =>
                {
                    TextBlock user_Name = FindChildControl<TextBlock>(homeSection, "user_Name") as TextBlock;
                    Image user_Image = FindChildControl<Image>(homeSection, "user_Image") as Image;
                    Debug.WriteLine("ID: " + fbSession.Token.AccessToken);
                    var profilePictureUrl = string.Format("http://ift.tt/1qxNyGU}", fbSession.Token.FacebookId, "square", fbSession.Token.AccessToken);
                    user_Image.Source = new BitmapImage(new Uri(profilePictureUrl));
                    user_Name.Text = String.Format("{0} {1}", (string)result["first_name"], (string)result["last_name"]);
                }, new System.Threading.CancellationToken(), TaskCreationOptions.PreferFairness, UISyncContext);
            };

            fb.GetTaskAsync("me");
        }

What am I doing wrong? How to fix this?