Equipped armor disappears when equipping other armor in the same slot

Diamond armor got deleted by iron armor when trying to equip.

I expected it to exchange the two different armors.

It deleted the armor that I was wearing.

Steps to Reproduce:
1. Equip with diamond armor (or anyting)

2. Get a different kind of armor and equip it without taking off the other armor.

3. The original armor will be deleted