Cannot write in the box in the Superflat presets option

Caused by the fix of MC-132281.

The bug

You won't be able to modify / write in the writing box while customising a Superflat world's preset.

How to reproduce

• Create New World
• More World Options...
• World type: Superflat
• Click on the option "Customise"
• Remove all the layers (optional)
• Click on the option "Presets"
• Try to modify / write in the writing box