Zombie Drops Carrot Instead of Rotten Flesh

I killed a zombie expecting Rotten Flesh as a mob drop.

What actually happened was a Carrot was dropped instead of Rotten Flesh. It only happened once, not sure if bug or rare drop.

Steps to Reproduce:
1.Kill a zombie with a diamond smite 1 sword.
2. If doesn't happen on first time, try and try again.