fix(mpd): Clear mpd error after getting error info
fix(mpd): Clear mpd error after getting error info

Before, polybar would crash, trying to throw a server error because
mpd_connection_get_server_error asserts that the error is of type server
error, but it isn't because it was cleared

jaagr/polybar,jaagr/polybar,jaagr/polybar,jaagr/lemonbuddy,jaagr/lemonbuddy,jaagr/lemonbuddy