cv2.error: OpenCV(4.2.0) /Users/travis/build/skvark/opencv-python/opencv/modules/imgproc/src/imgwarp.cpp:3391: error code example

Example: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

This error happened because the image didn't load properly.
So you have problem with the previous line cv2.imread my suggestion is :

check if the images exist in the path you give

check the count variable if he have valid number