Cast endpoint returning 404 for -some- anime

[Paul Chavarria]

[wojteb]

Atarashii API have strange error response policy. Changes are planed for v3.

This anime don't have characters, but have staff.

Second example: https://myanimelist.net/anime/35480/Karadasagashi/characters.

[Michael Johnson]

Fix 404 on Cast/Staff with only Staff

Controller logic required that characters/cast be present or gave a 404. Adjusted so that both staff and cast have to be empty to return a 404.

Fixes #152

→ <<cset 8de8d127dba5>>