To reproduce, define a closest hit shader. Define the ray payload as using a single half. Make sure to enable 16bit types in the DXC compiler. When trying to create a state object with this, the driver will fail with a null dereference in nvrtum64.dll. Replacing the half with a float results in success.
See attached project (C# .NET 8).
This occurs on Windows 10, with drivers 560.81, GeForce RTX 2080 Ti.
HalfRepro.zip (2.2 KB)