Program Terminates when there are more than 1 faces

Traceback (most recent call last):
File “FaceRecog.py”, line 76, in
face_selection=cv2.resize(face_selection,(100,100))
cv2.error: OpenCV(4.1.0) C:\projects\opencv-python\opencv\modules\imgproc\src\resize.cpp:3718: error: (-215:Assertion failed) !ssize.empty() in function ‘cv::resize’