No problem if the game is in Waco, and probably not if it's in Norman. Texas and Oklahoma do not have such assinine laws. They might have other's, such as bans on handguns in that trunk, although if you were "traveling" as I was Sunday and Monday, then you'd be OK. Since the gun is in the trunk, best it not be loaded, since you can't get to it all that quickly anyway.
It occurs to me that if Robinson's record is otherwise clean, this might be an excellent chance to test the law, all the way to the U.S. Supreme Court, if required, on 2nd and 14th Amendment grounds. Surely Robinson could easily afford any monetary penalty, but if there is potential jail time involved, he might not want to take the chance. Of course if the state decides to prosecute fully, he'll have no choice in the matter.