sms_composer could crash in case you didn't pass it the active_id,
active_ids context keys or don't call the default_get
In that case it would try to access `self.env[False]` which would crash
in the `_compute_recipients_count`
We also have to ensure that we have a default value for `self.res_ids`
because `literal_eval(False)` will crash
closesodoo/odoo#38545
X-original-commit: 7ed0bd258d8a744716101d89cfa0bdf0f7990fb5
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>