Windows player with a custom .exe file crashes in FixupD3D12SDKPath

Steps to reproduce:
1. Load UnityPlayer.dll from another application, and call into UnityMain
2. Observer a crash in FixupD3D12SDKPath

Forum post: https://discussions.unity.com/t/unity-as-a-library-dll-with-version-6/1557023

Reproducible with versions: 6000.0.0b15
Not reproducible with versions: 6000.0.0b14