Currently, if someone browses the website as incognito without login and registers to a free event then its attendee is created. However public user's partner is set as customer. With this commit booked_by field will be empty when registering to a free event without login. closes odoo/odoo#69810 Task-id: 2508558 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>