Abandon leads to invulnerable hero

In a recent game, a player on the opposing team abandoned in the first few minutes. Their hero was WK and he became invulnerable. The WK would follow us and attack, but we couldn't attack him. It was pretty annoying because it eventually ended up in our fountain and would chase us while we were trying to heal. Wouldn't have been too bad but we had 3 quitters on our team so 2 v 4 (plus this crazy WK).

Anything you can do about this? I'm not sure if the other team could or was able to control the WK. We could micro our abandons, but they could also die, unlike the WK.