[FIX] im_livechat: do not add public user to livechat channels

Public users (website visitors) do not need to be part of
a livechat channel to talk with the operator, they are using
a dedicated mechanism.
Explicitly including them is redundant and bloats the database.

addons/im_livechat/models/im_livechat_channel.py

@@ -166,7 +166,7 @@ class ImLivechatChannel(models.Model):
         operator_partner_id = user.partner_id.id
         # partner to add to the mail.channel
         channel_partner_to_add = [(4, operator_partner_id)]
-        if self.env.uid:  # if the user if logged (portal user), he can be identify
+        if self.env.user and self.env.user.active:  # valid session user (not public)
             channel_partner_to_add.append((4, self.env.user.partner_id.id))
         # create the session, and add the link with the given channel
         mail_channel = self.env["mail.channel"].with_context(mail_create_nosubscribe=False).sudo().create({