Do not moderate all members if moderation list is empty

[joecot]

No description provided.

[mpj17]

I am loathe to make a change that alters well established behaviour, even if that behaviour is broken.

There is actually a use-case for moderating everyone: a group goes toxic overnight (it happens) and the admin needs to slow everything down. If moderation was not such as borken system overall there would actually be a switch for this rather than relying on [] being everyone! Sadly, no one has been willing to do the hard yards in fixing moderation properly :(