[FIX] mail: Activity widget: undefined model
[FIX] mail: Activity widget: undefined model

Former implementation tried to retrieve the model in the 'model' and
'res_model' attributes of the widget, but both of them were undefined.

The model being required for some of the RPCs performed by the widget,
there were bugs (e.g. the messages weren't refreshed after the creation
of a new activity).

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