Assert "Failed to create inventory screen" when riding horse and doing command clear in Travelling Trader & Vanilla

Partner Rank: 4

Verification build: 1.15.0.51 3706814

Summary: Assert "Failed to create inventory screen" when riding horse and doing command clear in Travelling Trader & Vanilla

Impact: Asserts are bad and can result in failures during cert and content review if they're not caught and logged. While there is no apparent gameplay impact, it's clear there is something going wrong under the hood.

Repro:

1. Create a new world
2. ride a horse
3. do /clear

Observed result: Assert shown

Expected result: No assert
Screenshots attached: Yes, above