We should always ensure to assign something in a compute method Since sms_template_id is not required, we have to check that it is set before trying to render the template Also make sure to have a default value in case you don't have a res_id closes odoo/odoo#38546 X-original-commit: b96bb2a00737339dc53ff06167c1a0cd424ad717 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>