fixup! [IMP] sql_export_mail, add partner as export email recipient

Author: joepsanders

sql_export_mail/models/sql_export.py

@@ -181,5 +181,8 @@ def get_email_address_for_template(self):
         else:
             mail_users = self.mail_user_ids
             mail_partners = self.mail_partner_ids
-        email_addresses = mail_users.mapped("email") + mail_partners.mapped("email")
+        email_addresses = set(
+            mail_users.mapped("email") + mail_partners.mapped("email")
+        )
+        email_addresses.discard(False)
         return ",".join(email_addresses)