Put the summary of the bug you're having here

What I expected to happen was...:
I would spawn on the floating block when first-joining

What actually happened was...:
I spawned next to the block instead of on top of it and died.

Steps to Reproduce:
1. Create an empty, bottomless world
2. Fill in one block of your choice
3. Set the world spawnpoint on that block
4. Set the world to public
5. Join the world with an alternate account
6. You will spawn off of the block and fall to your death