baby zombies can be hit through wooden doors

Put the summary of the bug you're having here

What I expected to happen was...:
to aim down at the baby zombies and not be able to hit them through doors

What actually happened was...:
i hit a baby zombie at full sized zombie hight through a door

Steps to Reproduce:
1. spawn a baby zombie behind a door with a villager on your side
2. aim at the top half of the window
3. hit constantly (until it dies), so there's your problem