When I want to load a world from 1.12 the game crashes after few seconds,
Creating worlds directly in 1.13-pre5 work fine,
The world that i tried to launch is a superflat,
I tried to load the world with a server, it's also crashing,
Finally, I tried to convert the world in 1.13-pre4, it loads successfuly but when I switch in 1.13-pre5 the game still crashing.