In v15, in _find_members, we try to find a members with an email and without
partner_id or a member with the partner_id provided (if provided).
This commit remove the author_id, and so the partner_id to only looking for
members based on their email address.
Author_id could be the wrong since email is not uniq on partner.
We retrieve the same behavior than previously from this way.
courtesy of std for help to find a solution
closesodoo/odoo#80638
X-original-commit: 98d7b1417ee82fefcef175dd83ab41cd89db5119
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>