Red Graphical Glitch / Black screen when hitting a zombie wearing sapling:6

I was playing around with zombies with saplings on their head, when I accidentaly gave one a sapling with a damage value of 6, and nothing happened. When I attacked it to get rid of it, my entire screen got a reddish hue to it, and the shadows were all messed up. When I went into third-person, my skin was jambled. It went away after five minutes.

What I expected to happen was...:
I would make a zombie which would have a sapling on its head.

What actually happened was...:
I made a zombie that when you attack it causes a graphical glitch.

Steps to Reproduce:
1. Summon a zombie with a sapling on it's head with a data-value of 6.
2. Attack the zombie.
3. Notice the graphical glitches.