Wrong value returned in get_distinct

[ananace]

I'm getting big blocks of errors from Mopidy as it seems like calls to get_distinct are failing to return proper data, leaving a None value around the middle.

First what I assume to be a get_distinct('artist')

ERROR    SpotifyBackend backend returned bad data: Expected a list of unicode, not set([u'MIKA', u'Toto', ..., None, ..., u'Tears For Fears'])

And another one from what I can only assume is get_distinct('album')

ERROR    SpotifyBackend backend returned bad data: Expected a list of unicode, not set([u'90125', u'Toto', ..., None, ..., u'Happy Together'])