When a bed is placed, it doesn't check if the block below the top section is air.

What I expected to happen was...:
The bed should only be placed when the two blocks below where it will spawn are solid blocks.

What actually happened was...:
The bed only checks for if the block under the bottom half of the bed is solid. It will not check the top half.

Steps to Reproduce:
1. find a solid block with air surrounding it.

2. look at the top of the block and place a bed. The top half will hang over the side, disregarding the fact that there is an air block under it.