If you have items in your hotbar, open the creative inventory, and press Q over them to drop them out to the ground, the items get eliminated instead.

Steps to reproduce:

1. Place any block or item in your hotbar
2. Open the creative inventory
3. Drop the items from your hotbar while the inventory is open
4. Items will disappear instead of getting dropped

Exceptions: The "Survival Inventory" tab in the creative inventory (Chest icon) is not affected by this bug. Every other tab is.