Floating gravity-related blocks in world generation.

This bug is generated by some worlds with some specific seeds.

Reproduce

• Open Minecraft.
• Click Play
• Create a new world
• Repeat the previous step until the world generates floating sand/gravel

• • The bug unexpectedly reproduces.

What I Expected To Happen

The block upgrades and falls down as minecraft:falling_block.

What Happened

The sand of gravel was left in the air without being upgraded the block via tick.