Put the summary of the bug you're having here

What I expected to happen was...:
I thought mobs' and players' heads would sit inside of the glass block and not suffocate or be blinded.

What actually happened was...:
Mobs' and Players' whose head was inside the glass block wouldn't be able to see and would suffocate and die.

Steps to Reproduce:
1. Place a glass block at eye level above the ground.

2. For mobs, place the spawn egg under the block so that the mob spawns with its head inside the block.

3. For both players and mobs, place a rail under the glass block with a minecart on top.

4. Sit in the minecart or place a mob inside the minecart, so that the head of you or the mob is inside the glass block.

5. When in survival mode, your view will turn gray and you will suffocate and die.