There exists edge case on `reply_model`. when value of
`mail_messages.model` in database is empty then `mail_messages.model`
returns False, hence `reply_model` becomes False which raises
an error because _get_id does not accept a falsy values.
(because query: `SELECT id FROM ir_model WHERE model=false` has to
be run and model is char). Because of the fact that this query never
runs and fails opportunity is lost.
task-3248489
closesodoo/odoo#123488
X-original-commit: 6c0d2d7a9d44459f3e09a38bd80ef9b018e8c946
Signed-off-by: Stéphane Debauche (std) <std@odoo.com>