i've only seen this when looking up artists that don't exist in the MB database.

http example:
http://search.musicbrainz.org/ws/2/artist/?query=artist:easygroove&fmt=json
{"created":"2013-10-09T06:37:08.564Z","artist-list":{"count":0,"offset":0}}

https example:
https://search.musicbrainz.org/ws/2/artist/?query=artist:easygroove&fmt=json
{{

{"created":"2013-10-09T06:37:08.564Z","count":0,"offset":0,"artist":[]}

}}

shouldn't the response be the same in both cases?

edit: actually this does affect artists that exist as well. the returned json is quite different.