title: Null reference Error on AccessToken.CurrentAccessToken.UserID
body: <p>Using Unity editor currently to test FB Login.  Getting Null reference exception.  Will login once if I clear registry of all session details.</p>
  
  <p>Have tried some hotfixes previously found with SDK updates.  This is an older sdk as the version of unity the game was written for was 5.3.3</p>
  
  <pre><code>private void initSession() {
      Debug.Log("FbManager init session");
  
      string logType = PlayerPrefs.GetString("LoggedType");
      if (logType.Equals("Facebook")) {
          GameManager.Instance.facebookIDMy = 
  AccessToken.CurrentAccessToken.UserId;
          callApiToGetName();
          getMyProfilePicture(GameManager.Instance.facebookIDMy);
  
  
          LoggedIn = true;
  </code></pre>
  
  <p>Expect login to persist and be retrieved based on token stored in registry</p>