[BLOCKING LIVE CONTENT] Monster Battle Arena crashing in adventure mode.

Verification builds: Publish 1.4.0 891562
Summary: Monster Battle Arena crashes when an item is put into a hopper in the adventure modes.

Repro Steps:
0. install a fresh copy of Minecraft <- important to reproduce. Also been able to reproduce when it's the first thing i do when i open minecraft.
1. Download and start MBA
2. Press button for adventure mode
3. run to tims house
4. take a steak and run back to the first npc
5. put the steak into the hopper by the npc

Observed Results: game crashes, no assert error shows up (because publish build)

Expected Results: No crash.

Videos attached: https://youtu.be/9_tPD7q-Bp8