No person who is injured while getting on, or attempting to get on, a moving locomotive or railroad car, without authority from the owner or operator of the railroad, or who, having gotten on a locomotive or railroad car while in motion without such authority, is injured while so riding or getting off, shall recover any damages from the owner or operator thereof for such injuries unless proximately caused by an intentional act of such owner or operator with knowledge that serious injury is the probable result of such act, or with a wanton and reckless disregard of the probable result of such act.