[GAMEPLAY] Unable to walk on Karthus' corpse BUG

I was playing a custom versus 5 bots to test out the new Katarina. I killed the Karthus then waited out his passive since I was low. I then dove the second bot and W'ed to run out quickly (there was nothing to E to). However, when I clicked, my mouse was on Karthus' disintegrated form (after his passive runs out) which is equivalent to his dead body. My champion didn't move. I then clicked elsewhere and lived. I then tried clicking around and on Karthus' "body". It would NOT make the animated arrows or move me when clicking on him. I then tried this with the Ezreal corpse and it worked fine. It was certainly Karthus' corpse bugging out, disallowing me to move where I click. I COULD click on the other side of him and end up standing on his corpse, however.

Reproducing this bug: kill Karthus. Once his passive runs out, try to right-click on his ashes (where he died) to move there.