Fix playlist modifications
Fix playlist modifications

The strict PHP typing added in 4b180492 caused problems for playlist
modifications as there were some inconsistencies in the use of types in
PlaylistApiController.

paulijar/music,paulijar/music,owncloud/music,paulijar/music,paulijar/music,owncloud/music,owncloud/music,paulijar/music,owncloud/music,owncloud/music