There are two if statements in ProfaneWandUpdate.java that check if the contract has been depleted (well the first is an else if but it's just below the if that checks if the contract exists, so that doesn't really matter because the contract won't start empty), the first of which does a return; if true and the second of which seems to be responsible for wands reverting to wand cores upon contract depletion.

It's an ugly bit of code and I'm not entirely sure why I put that else-if return there, but the code does work as intended with the wand burning out at 0 contract. Not worth the trouble of cleaning the code at this point, anyway.