bug: KeyError in callback_balance when player disconnected

[em92]

Here is example: https://gist.github.com/lonewulfa/c20f0358670f91feacbd023d52c290c1

Player disconnected, his ratings info is wiped, then callback_balance is called attempting to access his wiped rating.

Possibly I need to add extra check if player is still playing before getting his rating info.

[em92]

Also related error: https://gist.github.com/lonewulfa/e710752872ac0ac802b1ab4825503bf1