MC-125872 has been fixed in 18w19a or + but this isn't the case in 18w22b or in 18w22c .The starting platform don't generate anymore in 18w22b or in 18w22c but not in 18w22a.
1.Create a superflat world
2.Go to customize
3.Select the preset "the void"
4.And the starting platform is not generated at all.