The bug

When creating a world with coordinate_scale set to 0, an error is given when preparing to create the world. However, this error does not prevent the user from creating the world.

During world creation and after every time the world is saved, the following error is shown in the game log:

dig
Server Thread
WorldGenSettings: Value 0.0 outside of range [9.999999747378752E-6:3.0E7]

While reproducing this issue, you may see duplicated entity errors within the game log.

When joining the world, you'll quickly notice that something's wrong. Even in creative mode, you won't be able to interact with the world. After entering the nether and re-entering the overworld using a nether portal, you will not be able to see the world (it will not load).

The only thing you'll be able to see is entities that were present in the nether. Hurting one of these entities locks the red glow onto them and you won't be able to interact with them again.

Upon rejoining the world, you spawn in the nether, still unable to interact with the world.

One may expect that the game should prevent them from creating a world with these issues, instead of giving them an error that does not block them from creating the world.

The custom world generation settings file used to reproduce this issue, 214372.json, is attached.