Closing the UI while having an item on the cursor no longer drops the item

The bug

Before MC-3587 was fixed when you closed the inventory while you had an item on the cursor, you had dropped the item. However now it will always put the item in your inventory. I (and proably many other people) have dropped items using this previously. I am not sure if this change is intended or not. I hope it isn’t.

How to reproduce:

1. Open your inventory
2. Click onto an item
3. Close the UI
   The item is not dropped unlike in previous versions.