This can potentially be returned as undefined, which is analytically annoying because then it turns into NaN and that's going all over the place.  I just traced it a bit and it seems harmless, but I think I'd be happier if we just did a "|| 1000" or something like that with a note that we are choosing an unreasonably high value until computed to avoid divide-by-zero problems or other annoyances.  Or really, any idea you have.  Or maybe just an XXX.