[FIX] mass_mailing: fix send with batch

This commit fixes a behavior when we send a batch of mailings
with no recipients.
When there is no recipients passed down, each mailing should
use it's own recipients and not the recipients of the first mailing.

closes odoo/odoo#75652

X-original-commit: 88d74fde5ce1ec70a88679429fda02180ce7fa81
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mass_mailing/models/mailing.py

@@ -666,8 +666,11 @@ class MassMailing(models.Model):
     def action_send_mail(self, res_ids=None):
         author_id = self.env.user.partner_id.id
 
+        # If no recipient is passed, we don't want to use the recipients of the first
+        # mailing for all the others
+        initial_res_ids = res_ids
         for mailing in self:
-            if not res_ids:
+            if not initial_res_ids:
                 res_ids = mailing._get_remaining_recipients()
             if not res_ids:
                 raise UserError(_('There are no recipients selected.'))