Seem it have some bugs when running train.py

[BlueSolarSystem]

"color.cpp:182:error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'."
And i searched for this error , it's seem we put a null frame to this function without checking . and then it occur .

Here are some details :
input.py line 66, in read_image
image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

And sorry for no format this code , i'm a new guy here.