PURPOSE Fix the 'multi' behavior when sending completion emails for slide.channels. SPECS There was a typo in the 'slide.channel#_send_completed_mail' method that prevented it from correctly working in "multi" mode. A new test was introduced to ensure the fix is working. LINKS Task 2170708 closes odoo/odoo#61004 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>