Pick-block creates ghost items in Creative when hotbar is full

To reproduce:

1. /clear or shift-click Destroy Item slot

2. Put an item in each of the 9 hotbar slots

3. Pick-block on a block that you don't have in your hotbar

You will have created a ghost item, namely the item that was pushed away from the hotbar to make space for the block. To verify this, /clear and open your survival inventory: The item will still be there.
Also you can't find this item with

/execute if data entity @p Inventory[{id:"minecraft:item_id"}]

until you open the inventory.