Unable to properly click items into the grey areas of the Creative inventory

Verification builds:
beta/1.2.10.1 | Windows 10: Yes

Summary:
Dropping an item into the grey area of the creative inventory should delete it. This has stopped working correctly in the 1.2.10.1 beta. It looks like the areas are not mapped properly now, so the items are either dropped on the ground, or are not removed at all.

This is a regression of MCPE-15674

Steps to Reproduce:

1. Open the creative inventory

2. Pick up a stack of items with the mouse

3. Right or left click the items in the grey area of the inventory

Observed Results:
Part of the grey area will allow items to be dropped on the floor, and the rest does nothing.

Expected Results:
Clicking an item on the creative inventory should just delete the item (as it does when clicking it onto other items in the inventory)

Screenshots/Videos attached: Yes

Notes: