Plugin crashes during startup when -RHIValidation is enabled

[TBBle]

Observed in Unreal Engine 5.4 and 5.5; I haven't tested older versions to see how they differ.

When -RHIValidation is passed to the engine, the GDynamicRHI global variable points at a proxy RHI implementation.

However, the XeSS Unreal Plugin in several places tries to static_cast<...>(GDynamicRHI), which produces an invalid result and crashes when -RHIValidation is in-use.

Instead, I believe it is safe all the way back to 4.27 to use static_cast<...>(GDynamicRHI->GetNonValidationRHI()).

[xessgamedev]

Thank you for reporting, we'll investigate the issue, and fix it in the next release.

[xessgamedev]

GDynamicRHI->GetNonValidationRHI() should be introduced in Unreal 5.0, but we still need to support Unreal 4.26 and 4.27.

To make it simple, we can disable XeSS when -RHIValidation is used, another reason is that we don't do plugin tests with -RHIValidation.
does it work for you? @TBBle