Fix some warnings

Hello

Here is a quick fix for this warnings

{"app":"PHP","message":"Undefined variable: array at apps\/music\/controller\/ampachecontroller.php#399","level":3,"time":"2014-03-25T21:13:52+00:00"}
{"app":"PHP","message":"Undefined variable: array at apps\/music\/controller\/ampachecontroller.php#399","level":3,"time":"2014-03-25T21:13:52+00:00"}
{"app":"PHP","message":"Undefined variable: user at apps\/music\/controller\/ampachecontroller.php#409","level":3,"time":"2014-03-25T21:13:52+00:00"}
{"app":"PHP","message":"Undefined offset: 2 at apps\/music\/controller\/ampachecontroller.php#421","level":3,"time":"2014-03-25T21:13:52+00:00"}
{"app":"PHP","message":"Undefined offset: 3 at apps\/music\/controller\/ampachecontroller.php#421","level":3,"time":"2014-03-25T21:13:52+00:00"}

Regards,
Xéfir Destiny