[FIX] mail: variable not referenced before assignment

In case of generic activity user type, if the referenced field does not exist
in the linked model, we should not raise an UnboundLocalError and use the
current user as a fallback case instead.

closes odoo/odoo#50802

X-original-commit: 554a7cc400b4e1d8cda835e445b152f146bb0003
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>
Signed-off-by: Alex Tuyls <alt-odoo@users.noreply.github.com>

addons/mail/models/ir_actions.py

@@ -126,6 +126,7 @@ class ServerActions(models.Model):
         if action.activity_date_deadline_range > 0:
             vals['date_deadline'] = fields.Date.context_today(action) + relativedelta(**{action.activity_date_deadline_range_type: action.activity_date_deadline_range})
         for record in records:
+            user = False
             if action.activity_user_type == 'specific':
                 user = action.activity_user_id
             elif action.activity_user_type == 'generic' and action.activity_user_field_name in record: