Fix user.player

[carlosefonseca]

When doing user.player, I'm getting the error NoMethodError: undefined methodpresent?' for #`. Since no other method seems to be using this check before parsing the response, I'm suggesting its removal.

[carlosefonseca]

I've updated the PR since I found that if Spotify can return an empty response (nothing is playing) and it would return nil instead of a Player object, not allowing the play methods to be called.

[guilhermesad]

👍