so as it said in the title in superflat worlds under 'The Void' Preset in the south-eastern corner of the spawn platform a block is missing right at the corner as seen in the attached screenshot.

How To Reproduce:

1. Click  on 'Singleplayer'
2. Click 'Create New World'
3. Click 'More World Options...'
4. Change 'World Type' to 'Superflat'
5. Click 'Customize'
6. Click 'Presets'
7. Choose 'The Void'
8. Click 'Use Preset'
9. Click 'Done'
10. Click 'Create New World'
11. Go to The South-Eastern Corner Of the Spawn Platform
12. Then you should see that there is a block missing