"Force password change" throws SQL error [#2241489]

Hi! I just enabled password_policy on an Ubercart 2.13-6.30 site. I didn't get any errors on the enable, but when I tried to force all users to change their password, I got this error:

    Warning: array_fill(): Number of elements must be positive in db_placeholders() (line 276 of [path]/pressflow-6.30.1/includes/database.inc).
    Warning: implode(): Invalid arguments passed in db_placeholders() (line 276 of [path]/pressflow-6.30.1/includes/database.inc).
    User warning: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near &#039;)&#039; at line 1 query: UPDATE password_policy_force_change SET force_change = 1 WHERE uid IN () in _db_query() (line 169 of [path]/pressflow-6.30.1/includes/database.mysqli.inc).

Looking again, I realized that one of the roles, "product_role", is provided by Ubercart, and this site does not actually have any users with that role.

So, I tried to force a password change again, using only those roles that have users. This did not throw an error.

But when I tried to force a password change only for "product_role" users, I got the error again.

So, I wonder if this is a general bug that occurs whenever a password change is forced on a role with no users. If so, it could probably be fixed with a quick check.

Thanks!