Material doesn't have a float or range property '_DrawOrder' errors are thrown on assigning any material to Decal Projector in prefab mode.

Steps to repro:
1. Create a new HDRP project
2. GameObject > Rendering > Decal Projector.
3. Create a prefab > Open in Prefab mode.
4. Assign any material to Decal Projector

Actual Result:
Material doesn't have a float/range errors are thrown in the console.

Expected Result:
No errors in the console.

Reproducible in:
2020.2.0a9, 2020.1.0b8, 2020.1.0a23 with Package Version 9.0.0, 8.1.0, 8.0.1.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stack trace:
Material doesn't have a float or range property '_DrawOrder'
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr, Boolean&)