It looks like Gio's arm is bowed out away from his body and it strikes his arm. I need to go and find another replay that allows me to freeze-frame it better, but IMO this should be a handball.As I understand it, if your arm/hand is in a natural stationary position against your body, and the ball hits it, that's fine. But if your arm/hand is held outward, for any reason (running, balance, etc), then the ball hitting it will be called whether there was movement of the arm/hand or not.