As detailed in https://github.com/xbmc/xbmc/pull/13051, Kodi v18 changes the way album genres are handled, as the genre (by which i mean `genreId`) ceases to be available at the album level, being only available at the songs level.
This impacts Kore because `GetAlbums` and `GetAlbumDetails` won't return the `genreId` tag, from which the local AlbumGenres table was populated.
This PR changes the source of the local AlbumGenres table to be the `genreId` returned at the song level (by `GetSongs`), to make it somewhat more consistent with the way Kodi will handle things from now on.
246693a7cc