Items held with the cursor will drop upon death with the keepInventory gamerule enabled

When a player dies while holding any item(s) in their mouse cursor (in an inventory, or GUI for example) the stack will be removed from that player's inventory and drop as an item entity, even if the keepInventory gamerule is enabled.

Steps to Reproduce:

^{(Must be in survival mode, with cheats enabled)}

1. Enable 'keepInventory':

   /gamerule keepInventory true
   

2. Take continuous damage (ie; stand near a cactus, in fire, falling. etc)
3. Before dying, open your inventory and hold an item in your cursor

Expected & Observed Behavior:

- What ever you're holding will drop on the ground as an entity where you died.
- The items would be returned to the player inventory.