nvapi: Guard against null device in Reflex calls

[Saancreed]

Fixes a crash in Horizon Forbidden West.

[esullivan-nvidia]

Maybe it would be better to have the Reflex NVAPI entry points return NVAPI_INVALID_ARGUMENT if the device is null?

[Saancreed]

Maybe it would be better to have the Reflex NVAPI entry points return NVAPI_INVALID_ARGUMENT if the device is null?

Yeah, good point. I intend to also check how native NVAPI behaves on Windows here first but something like NVAPI_INVALID_ARGUMENT or NVAPI_INVALID_POINTER sounds likely to be the case.

[Saancreed]

Native Windows NVAPI returns -5 / NVAPI_INVALID_ARGUMENT for NvAPI_D3D_* Reflex entry points accepting device as IUnknown* and -14 / NVAPI_INVALID_POINTER for NvAPI_D3D12_* Reflex entry points accepting ID3D12CommandQueue*. I updated each relevant function to behave like this and added tests to verify this behavior.

I've kept the null check in GetLowLatencyDevice for general robustness, even though it shouldn't be needed anymore. We can probably drop that commit though.

[jp7677]

Reference: ValveSoftware/Proton#7590