[FIX] mail_show_follower: Company identification in _send()

Before this commit, 'Show Internal Users CC' would always be False,
regardless of the setting in the company, in case the message came
from a record with a company_id field but without a value assignment to
it (e.g., a partner record with no company), as company would be an
empty record.

This commit fixes the behavior by capturing company from self.env in
these cases.

mail_show_follower/models/mail_mail.py

@@ -73,7 +73,9 @@ def _send(self, auto_commit=False, raise_exception=False, smtp_session=None):
             # recipients from any Notification Type (i.e. email, inbox, etc.)
             recipients = mail.notification_ids.res_partner_id
             record = self.env[mail.model].browse(mail.res_id)
-            company = getattr(record, "company_id", self.env.company)
+            company = getattr(record, "company_id", False)
+            if not company:
+                company = self.env.company
             show_internal_users = company and company.show_internal_users_cc
             show_in_cc_recipients = recipients._filter_shown_in_cc(show_internal_users)
             if len(show_in_cc_recipients) <= 1: