Starting a new superflat customized world with this preset: 3;7,3*1,52*24:2,31:1;21;
and a random seed, cheats on, structures off, bonus chest off, creative, I expected to start playing and after creating the world start playing.

The game crashes to Launcher ang gives a crash report.

The world was created successfully i thing, 'cause it is still in the list of Single Player Worlds, but each time i try to access again, crashes to launcher.

The steps to reproduce are the ones i just described.