Nah, none of that. Just your charger gets bricked so not knowing which one of the wires are positive and negative going to be the least of your worries from that point on.
That's the theory. I have seen smoke coming out of a charger when the 5v DC side got short circuited due to wire damage. Quickly unplugged obviously, but I assume there was a real possibility of the AC side shorting if things melt inside the charger.
