Steps to reproduce

1. Die in Hardcore mode
2. Click on delete world button
3. Game should return to main title with white background.
4. When on world select, that world will be there.
5. Try to delete that world.
6. Game should display delete dialog, with world as background.
7. Click 'Delete'.
8. World will delete.
9. When trying to create new world, game will hang on black screen.

Logs when trying to delete world in 2nd step:

[14:15:19] [Client thread/INFO]: Deleting level Nowy świat

[14:15:19] [Client thread/INFO]: Attempt 1...

[14:15:19] [Client thread/WARN]: Couldn't delete file D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region\r.-1.-1.mca

[14:15:19] [Client thread/WARN]: Couldn't delete directory D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region

[14:15:19] [Client thread/WARN]: Unsuccessful in deleting contents.

[14:15:19] [Client thread/INFO]: Attempt 2...

[14:15:19] [Client thread/WARN]: Couldn't delete file D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region\r.-1.-1.mca

[14:15:19] [Client thread/WARN]: Couldn't delete directory D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region

[14:15:19] [Client thread/WARN]: Unsuccessful in deleting contents.

[14:15:20] [Client thread/INFO]: Attempt 3...

[14:15:20] [Client thread/WARN]: Couldn't delete file D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region\r.-1.-1.mca

[14:15:20] [Client thread/WARN]: Couldn't delete directory D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region

[14:15:20] [Client thread/WARN]: Unsuccessful in deleting contents.

[14:15:20] [Client thread/INFO]: Attempt 4...

[14:15:20] [Client thread/WARN]: Couldn't delete file D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region\r.-1.-1.mca

[14:15:20] [Client thread/WARN]: Couldn't delete directory D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region

[14:15:20] [Client thread/WARN]: Unsuccessful in deleting contents.

[14:15:21] [Client thread/INFO]: Attempt 5...

[14:15:21] [Client thread/WARN]: Couldn't delete file D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region\r.-1.-1.mca

[14:15:21] [Client thread/WARN]: Couldn't delete directory D:\MultiMC\instances\19w12a\.minecraft\saves\Nowy świat\region

[14:15:21] [Client thread/WARN]: Unsuccessful in deleting contents.