It crashes because the `i` variable isn't initialised properly at the top of the function (line 596), so it gets any old value left in it, 1288 in my test. When control falls through this if block, it ends up passing through to line 828 ("check for a valid item ID"). All the other else blocks that fall through to this line set an item ID, so 836 tries to look up item ID 1288 which is well past the end of the array.