When you have the night vision and blindness effects at the same time, you can't see anything.

When I used /effect commands to give myself blindness and night vision, I couldn't see anything AT ALL. It wasn't like the normal blindness effect where you can still see stuff close to you, everything was completely black. I gave myself level 1 of each effect for 30 seconds. The commands were:
/effect 12_Me_21 15
and
/effect 12_Me_21 16
(12_Me_21 is my username)
When I drank milk to remove the effects, everything looked normal again.
I tried it in version 1.6 and it still happened, I think it has been around for a long time. It might not actually be a bug, because having blindness and night vision at the same time is not really supposed to happen anyway.