Step to Reproduce:

        1.Take a slate in the creative mode inventory and place on the floor in the pervious version

        2.Exit the game and update to the latest Beta/Preview

        3.Rejoin the world and check the slate

Obversed Result:

        The slate is disappeared in the creative mode inventory, but it can still be used in the game while in the inventory.

Excepted Result:

        The slate is disappeared in the inventory and the slate block turns the air.