Thanks Jere!
When attempting to move while affected by a net, there is some code which checks whether an interactable is in the next tile. If there is, it allows the move which will flow on to interact instead of actually move - otherwise the move is prevented. When dying, the same code moves creatures to a null tile which causes the above check to throw a null pointer.
I've added a new post-challenge download to the downloads page which fixes this issue. Everything else seems pretty stable so that's the only post-challenge change so far!