[FIX] mail: require res_model_id on followers
[FIX] mail: require res_model_id on followers

The flag has been forgotten with 94d2b97da4af28c551d246f14347f7674c4d50f5

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo