crash bug from clicking customization in superflat while creating new world

https://youtu.be/ko6OhRds-go (Didn't do it in fullscreen to show what version i was using [EDIT: lol i had the thing blocking the version........ derp!!!!! oh well, I show the versions afterwards anyways so.....])

Okay, so the issue is that I can't use the customization feature to make a superflat world, or else the game would crash when i click it.