What happens if all five bands' images don't exist?

[suchyta1]

If any of r, i, z don't exist, the RunTileJob.py code doesn't even keep that tile, because a detection coadd can't be built. I think this is reasonable behavior. If g or Y doesn't exist, the code is supposed to run normally, but push nulls the DB for where these measurements nominally would be. Again, these seems sensible to me. But the reason this is in issues is this is totally untested, and not high on my todo list at the moment, so may remain untested for some time.