Pressing enter in the name or seed field on the create world dialog no longer creates the world

The bug

As of snapshot 17w43a, pressing enter in the name or seed field on the create world dialog no longer creates the world.

How to reproduce

1. Open the new world GUI

2. Click on and then type a world name into the name field

3. Press enter. Observe that nothing happens.

4. Switch to the more options page

5. Click on and then type a seed into the seed field

6. Press enter. Observe that nothing happens.

7. Click outside of the text field so that it is no longer focused

8. Press enter. The world will be created.

In prior versions pressing enter would work even if the field was focused.