Comment 2 for bug 943709

Coverity is right about the potential NULL dereference -- it looks like maybe (!x && !y) could be replaced with (!x || !y).

Even though the bug exists, it doesn't look like any of stack_get_slot_position()'s callers ever trigger it.

Apologies in advance if I'm stepping into someone else's code here... I've just been looking through the Coverity tickets to see what kind of issues or nonissues it's reporting :)