Weird bug that the world is just sky and my avatar just flowing in the air.

What I expected to happen was...:
I wanted just to play in my minecraft world and I did not expect this....

What actually happened was...:

I  joined my world in 1.16.1 and when i joined my world, it just didn't backup and i was flying in the air. can you please help me with it? i tried to join my other worlds but it did the same thing
and yes, i tried to close minecraft and open again but it didn't work.
Steps to Reproduce:
1. Open minecraft with Optifine 1.16.1 
2. Open your 1.16 world
3. then after you saw the bug, try to open other world that is 1.16.1 or 1.14.4 (i tried these two)