[FIX] website_forum: avoid traceback on ack notif
[FIX] website_forum: avoid traceback on ack notif

Before this commit, notification_read raise a traceback on some button click.
Eg: Flag/unglaG

It was hidden in the console, but we can just avoid it too

closes odoo/odoo#30524
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo