I was just running along in a survival world when the game crashed. I loaded it up again. Crash. It has done this every time without fail. Here's the crash report for the most recent one.
MC-129780
Chunk Generation Crash
Resolved
Duplicate
0
John
(Unassigned)
Unconfirmed
Minecraft 18w20b
Retrieved
If you need the other crash reports, I'd be glad to post them.