Cycling through the shaders various ones give you a solid black screen. Clicking the button again will sometimes give you a working shader again. I found this bug while recording my 13w39a snapshot video. You can view it once it finishes uploading at: http://youtu.be/mFFqiW_3EWk

Only 3 shaders seem to be affected:
art.json
ntsc.json
phosphor.json