[Yt-dev] parallel profiler problem

[Matthew Turk]

> So, how do I make it skip that halo? I see there is a len(sphere._grids) == 0 test, but this case there are two grids so it passes that.

I think the problem might be with the bounds.  If no points within the
sphere satisfy the radius bounds, it will fail.  I will commit the
changes in that patch I sent you and then we can insert a try/except
block for the exception I added; that is the pragmatic solution, I
think.  But I really, *really* think we need to figure out why the
radius bounds are not giving us any points.

-Matt