I was doing some experiments in this New snapshot, The world this crash happened in was me putting Super flat chunks into a Normal world to see all the layers of the world from the update. I was looking at the edge and the game randomly crashed. It came up with "Game crash" in launcher and I got the crash report.
How to reproduce
1. Create a new World with Generator Default
2. Create another world with Superflat Generator
3. Copy the region files from Superflat world to Normal Generator world
4. Explore around in Normal world and game crashes randomly.
Expected behaviour
World doesn't crash
Editing save files is not supported.