Bug Description

Issue when integrating OAuth with different services such as Github. Note that I'm using database for the User instead of Stache. Looking at the Stache\UserRepository, it seems the findByOAuthId() is implemented correctly.
The error message is
TypeError Return value of Statamic\Auth\Eloquent\UserRepository::findByOAuthId() must be an instance of Statamic\Contracts\Auth\User or null, none returned

How to Reproduce

I followed the steps on the Statamic OAuth page

1. Added oauth provider to statmic/oauth.php
2. Add provider credential to config/services.php
3. Update config/statamic/oauth.php with the service
4. Add login redirect route and callback route in config/statamic/oauth.php.
5. Try to login using Github from CP or try logging in with {{ oauth:github }} from frontend.

Extra Detail

Environment

Statamic version: 3.0.0 Pro

PHP version: 7.3.21

Install method (choose one):

• Fresh install from statamic/statamic