Minor bugfixes

[neophob]

clear artist if metadata changes, disable double emit

[jishi]

Hm, I don't think we should remove the player emit here, since I emit on both player and the discovery explicitly to allow subscription to either one depending on need. Where do you see the double emits? The only thing in the HTTP API that uses the events, are the new webhook functionality. Could it be your code that has bound events to both players and the discovery object somewhere?

[neophob]

invalid