World Name not updated in GUI after renaming

Hi,

I just noticed that the GUI doesn't update the name of a renamed world.

Steps to reproduce:

1. Load in Minecraft Snapshot 18w30b (as it did work fine in the Release Version 1.13)

2. Rename a World and hit Save

3. See that the world name did not update

4. Restart the Game

5. Now the world name got updated

The attached picture shows this on a renamed world.