Spawning in the air after creating a new world

A Spawn bug in Minecraft 1.4.1 pre

What I expected to happen was...:
Normaly you spawn in the ground

*What actually happened was...:
Sometimes when i create a new world and spawn, i spawn in the air so i take fall damage.
I dont know if this is a bug or it ment to be there.

Steps to Reproduce:
1. Create a new world
2. Spawn
3. Take fall damage becouse of spawning in the air