replaceitem command syntax has changed causing functions to fail

Partner Rank: 1

Verification builds: Beta 1.12.0.2 release 2039725

Summary: replaceitem command syntax has changed causing functions to fail. As of 1.12 it no longer allows "air" to be used

Use case: Breaks several maps that use this command in this way, including Play: City Mall

Repro Steps:

• Open City Mall
• Note the function failure
• alternatively, open a new world with cheats on
• Do replaceitem entity @s slot.weapon.mainhand 0 air 1 0

Observed Results: The command fails as air is no longer a valid block to use.

Expected results: The command should succeed as it has for many versions.

Screenshots/Videos attached: Yes

Notes: