I created a superflat world with bedrock being the only layer.
What happened was the world glitched out (blocks were disappearing and the bedrock texture started distorting)
Steps to Reproduce:
1. Make a superflat world, with bedrock being either the only and/or top layer.
2. Place a few blocks (I used Stone) side by side.
3. Watch as the glitchy madness unfolds!
Please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report (minecraft/crash-reports/crash-<DATE>-client.txt) here. Screenshots would also be helpful.