Item duplication while a screen is opened (Creative Mode)

Description

If you try to drop an item stack while a handled screen is opened and you are in creative mode, the item(s) you've dropped will get doubled. This only works in creative mode.

Even stranger things happen in your creative inventory. If you drop a single item, and the remainder of that stack stays in your inventory, it'll get duped, while dropping an entire stack (CTRL + drop) won't do anything.

Observed Behavior

The size of the item stack dropped gets doubled.

Expected Behavior

The item stack stays the same.