[FIX] mail: invite only channel channel

It is not interesting to be able to add chat channels to document.

addons/mail/wizard/invite.py

@@ -28,7 +28,8 @@ class Invite(models.TransientModel):
     res_model = fields.Char('Related Document Model', required=True, select=1, help='Model of the followed resource')
     res_id = fields.Integer('Related Document ID', select=1, help='Id of the followed resource')
     partner_ids = fields.Many2many('res.partner', string='Recipients', help="List of partners that will be added as follower of the current document.")
-    channel_ids = fields.Many2many('mail.channel', string='Channels', help='List of channels that will be added as listeners of the current document.')
+    channel_ids = fields.Many2many('mail.channel', string='Channels', help='List of channels that will be added as listeners of the current document.',
+                                   domain=[('channel_type', '=', 'channel')])
     message = fields.Html('Message')
     send_mail = fields.Boolean('Send Email', default=True, help="If checked, the partners will receive an email warning they have been added in the document's followers.")