xBRZ black screen when High resolution scale >1

[arandomguysomewhere]

Hi, thanks for this great emulator! I'm not sure if this issue is emulator-specific but when using either of the xBRZ shaders on the OpenGL renderer, if the High resolution scale is greater than 1 the graphics output is a black screen. Maybe there's an underlying bug or a warning about combining scaling with resolution scaling could help if not?

[endrift]

I should probably add a warning that upscalers don't mix well with highres, but it still shouldn't just be black.