Repro steps :
- Open attached project
- Open SampleScene
- Make sure PathTracer is enabled in the volume gameobject
- Select Shader Graphs_StackLit_Parameter and change its parameter called coat mask to 0

Expected : Coat should disappear
Result : Material's all black

Additional info :
- When doing the same without using a parameter in shader graph, it does not repro.. (you can test on Shader Graphs_StackLit_Hardcoded).
- It reproes only with the exposed parameter
- This looks like it's very niche issue but this actually makes the 3dsMaxPhysical Material fail !

Environment :
- Windows 10
- Unity 2022.1.0a13
- HDRP 13.1.1