Error checking for send-to-role

Issue Summary

Had module configured to send to a particular email address and also a role, but there was nobody in the role. Result was "unable to send email...." error when users registered, even though they were getting the usual verif. email themselves.

Would be slick if the module could check for that on the config page and indicate "there is nobody in that role" or something.

Better yet, it could just gracefully ignore the role if nobody is in it?

(I'm not entirely sure, but I think that the send notify email address doesn't get the email in this scenario either.... so having an empty role may be breaking the whole send process)