Before 1.16.100, you could do /replaceitem entity user slot.weapon.offhand 1 fireworks 1 1
and it would put a firework with flight duration 1 in your offhand. Now, it puts a firework in your offhand with no duration at all. If these fireworks are used with a crossbow, the fireworks are fired vertically instead of horizontally.

Steps to Reproduce:

1. Type /replaceitem entity @s slot.weapon.offhand 1 fireworks in the chat
2. Open your inventory
3. Hover over the fireworks

Observed Results:
The fireworks have no flight duration.

Expected Results:
The fireworks should have a flight duration of 1.