bp_user_has_opted_out() should return false if no email address is provided.

[dcavins]

bp_user_has_opted_out() uses BP_Optout::optout_exists() internally, but if no where parameters are provided, BP_Optout::get() returns every optout, as you might expect.

This is weird behavior for bp_user_has_opted_out(), though (and for optout_exists, truthfully). We prevent this issue in bp_add_optout() by ensuring that the email address parameter is not empty, so we could add a similar check in bp_user_has_opted_out().

[dcavins]

If no email address parrameter is provided, bp_user_has_opted_out() should return false.

[dcavins]

In 13909:

Change bp_user_has_opted_out() behavior.

Our function bp_user_has_opted_out() should return false if no email address is provided.

The underlying issue is that if you pass no where filter arguments to BP_Optout:: optout_exists() (which uses BP_Optout::get()), you get every optout back, which is the wrong answer in this case.

Props emeralive.

Fixes #9172.