Placing item in beacon "fuel" slot then exiting GUI drops item on ground, unlike other GUIs

If you place a mineral item (diamond, iron ingot etc) into a beacon's "fuel" slot then exit the GUI without clicking the "Done" button, the item will be thrown on the ground. This is inconsistent with the newer behavior of other GUIs that do not store items (such as the crafting table, enchanting table or villager trading screen), where the items in the screen are directly added back into the inventory when closing the GUI.