When hooks are used to work with attachments, the id_msg is 0.  This can sometimes cause the attachment to still be loaded.  Prevent us from directly loading attachments with id_msg = 0 unless a hook has handled this already.
When hooks are used to work with attachments, the id_msg is 0.  This can sometimes cause the attachment to still be loaded.  Prevent us from directly loading attachments with id_msg = 0 unless a hook has handled this already.

StealthWombat/SMF2.1-more-forkery,StealthWombat/SMF2.1-more-forkery