PHP Warning: Undefined variable $user in class-guest-contributor-role.php on line 271

[ronchambers]

Describe the bug

On line 271 ( link ) the variable $user is undefined. I assume it should be $user_or_name->user_login.

From debug.log:

PHP Warning:  Undefined variable $user in /includes/plugins/co-authors-plus/class-guest-contributor-role.php on line 271
PHP Warning:  Attempt to read property "user_login" on null in /includes/plugins/co-authors-plus/class-guest-contributor-role.php on line 271

I would have done a pull request, but I wasn't sure if wrapping the code in is_object() would make sense and then making the string version the default return value. Or possibly keeping is_string and adding is_object, then returning a random string if neither.

To Reproduce
Steps to reproduce the behavior:

1. Go to /wp-admin/user-new.php
2. Choose "Guest Contributor" in the "Role" drop down.
3. Add user with just a "Display Name", all other fields blank.
4. View warning in debug.log.
5. View db wp_users.user_email and see that the email is blank. (I'm not sure if this is OK or not).

Expected behavior
There should be no error in debug.log.

[ronchambers]

@leogermani @adekbadek - If you'd like me to fix, let me know :-)