coding_error displayed on login through Facebook when account has been created using a mobile number

Getting the following error when logging in through Facebook using a Facebook account that has been created using a mobile number.

Coding error detected, it must be fixed by a programmer: The 'username' value must be set in other.

More information about this error

×Debug info: 

Error code: codingerror

×Stack trace:

line 112 of /lib/classes/event/user_login_failed.php: coding_exception thrown

line 272 of /lib/classes/event/base.php: call to core\event\user_login_failed->validate_data()

line 372 of /auth/oauth2/classes/auth.php: call to core\event\base::create()

line 49 of /auth/oauth2/login.php: call to auth_oauth2\auth->complete_login()

×Output buffer: <br /> <b>Notice</b>: Undefined index: username in <b>/home/jun/moodles/im_review/moodle/auth/oauth2/classes/auth.php</b> on line <b>371</b><br />

This issue has initially been raised in the forums: https://moodle.org/mod/forum/discuss.php?d=354142

To reproduce:

1. Create a sample FB app: https://docs.moodle.org/33/en/OAuth_2_Facebook_service
2. Create a FB account using your mobile number.
3. If your FB account is different from the account you used for FB app, assign the FB account with a Tester Role to the your FB App.
4. Enable OAuth2 authentication plugin on your Moodle site.
5. Go to Site administration / Server / OAuth 2 services and create a new Facebook service.
6. Enter your FB app's App ID and Secret to the Client ID and secret fields.
7. Login to Moodle using your Facebook account.
8. Expected:
   • After the FB authentication process, you should be redirected back to Moodle and get logged in.
9. Actual:
   • The error message above is encountered.