Chicken Jockey spawns when villager died

Put the summary of the bug you're having here

A chicken jockey can spawn when an adult was killed by a zombie and transformed into a zombie.

What I expected to happen was...:
Describe what you thought should happen here

I thought that this isnt normal because a BABY zombie villager is riding a chicken and an ADULT villager was killed.

What actually happened was...:
Describe what happened here

I was recording tips and tricks, then this accidently happened...

Link for the video with the EVIDENCE: https://www.youtube.com/watch?v=KL2JAMp1AXc 2:02 <The moment when it begun

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. I dont know, just fix it.
3. ...