Being killed after the nexus has been destoyed

This Video yet old but still relevant is an example of what happened to me. You should not be able to die after destroying the nexus! I'm in my placments and my KDA is important this season, I'm really try hard mode right now so being dropped from a 6 to a 4 KDA just because of a bug where you destroy the nexus but poppys sunfirecape kills you....? while you still have your E playing as fizz but cant use it cause the games ended... like XD pleas riot do something about it its very frustrating!