[FIX] mail: do not try to send email to partners without email

As `formataddr` only accept strings as arguments, an exception was
raised when trying to notify a mailing list channel with followers
without email.

closes odoo/odoo#30492

addons/mail/models/mail_channel.py

@@ -352,7 +352,7 @@ class Channel(models.Model):
         # real mailing list: multiple recipients (hidden by X-Forge-To)
         if self.alias_domain and self.alias_name:
             return {
-                'email_to': ','.join(formataddr((partner.name, partner.email)) for partner in whitelist),
+                'email_to': ','.join(formataddr((partner.name, partner.email)) for partner in whitelist if partner.email),
                 'recipient_ids': [],
             }
         return super(Channel, self)._notify_email_recipients(message, whitelist.ids)

addons/test_mail/tests/test_mail_channel.py

@@ -155,7 +155,15 @@ class TestChannelFeatures(common.BaseFunctionalTest, common.MockEmails):
         """ Posting a message on a mailing list should send one email to all recipients """
         self.env['ir.config_parameter'].set_param('mail.catchall.domain', 'schlouby.fr')
         self.test_channel.write({'email_send': True})
-        self._join_channel(self.test_channel, self.user_employee.partner_id | self.test_partner)
+
+        # Subscribe an user without email. We shouldn't try to send email to them.
+        nomail = self.env['res.users'].create({
+            "login": "nomail",
+            "name": "No Mail",
+            "email": False,
+            "notification_type": "email",
+        })
+        self._join_channel(self.test_channel, self.user_employee.partner_id | self.test_partner | nomail.partner_id)
         self.test_channel.message_post(body="Test", message_type='comment', subtype='mt_comment')
 
         self.assertEqual(len(self._mails), 1)