Put the summary of the bug you're having here

What I expected to happen was...:
I would equip the elytra from my hotbar and my chestplate would then ocupy the space in my hotbar where the elytra was

What actually happened was...:
equipping the elytra from the hotbar left me with an empty hand, and the chestplate was nowhere in my inventory

Steps to Reproduce:
1. Put a chestplate on
2. put an elytra in your hotbar
3. right click with the elytra in your hand to equip it