Hopper minecarts absorb the item stack thrown by a creative player using Q button with GUI open twice causing item duplication

What I expected to happen was...:
Hopper minecarts get the same amount of items thrown by the player

What actually happened was...:
Hopper minecarts get twice as the amount of items thrown by the player

Steps to Reproduce:
1. Switch to creative mode
2. Place down a hopper minecart
3. Right click it and then press Q to throw an item
4. You will find the item Duplicated

Dragging the item to throw it won't work