If you have an artist with no fan art, and then go download some to place into the fanart folder, you'll discover that the API (and perhaps also the web app) has already cached "no art", so it continues to return an empty array until you recycle API.
If you have an artist with no fan art, and then go download some to place into the fanart folder, you'll discover that the API (and perhaps also the web app) has already cached "no art", so it continues to return an empty array until you recycle API.