[Breaks live content] Slabs with can_place_on tags cannot be placed

Verification builds: v1.5.0 (live)

Summary: Wooden and stone slabs with can_place_on tags cannot be placed in the world by players in adventure mode.

Impact: Several building challenges in Blitz Build, Blitz Build Summer, and Blitz Build demo all rely on can_place_on tags, preventing many of the levels from being completed.

Repro steps:

1. Enter adventure mode: /gamemode 2 @p

2. Give yourself a wooden slab with a can_place_on tag: /give @p wooden_slab 1 0 {"minecraft:can_place_on":{"blocks":["grass"]}}

3. Try to place the slab on a grass block

4. Give yourself a stone slab with a can_place_on tag: /give @p stone_slab 1 0 {"minecraft:can_place_on":{"blocks":["grass"]}}

5. Try to place the slab on a grass block

Observed Results: Neither slab can be placed, and when you try to place the stone slab, a mysterious black box appears above where you click for a second before fading away.

Expected results: Slabs should be able to be placed on blocks defined in the can_place_on tag.