Error: (-215: Assertion failed) !_scr.empty() in function 'cv::cvtColor'

Hi

I'm having error when running processing the pictures. Error screen reads as attached file 1.png processing photos while having this error as attached file 2.png

I saved this project under below route C:\Users\edz\Desktop\ailab-master\VirtualStage\BackgroundMatting

would you be able to help solving this issue?

thanks.