Reminder email sent to members without active membership

[myself248]

It appears that the "send billing emails" button sends email to members who have a nonzero balance, even if all their memberships have end-dates in the past. If this is behavior as designed, it'd be nice if it was documented more clearly! Currently it's necessary to falsely-zero the accounts of anyone who's left so that we don't bother them.

I think if someone doesn't have an active plan, the email shouldn't bother them. It should be possible to keep their delinquent balance (at the treasurer's discretion) in case they come back.