AttributeError: 'NoneType' object has no attribute 'shape'

[pvsv]

import imutils
import time
import cv2
import csv
import os

cascade = 'haarcascade_frontalface_default.xml'
detector = cv2.CascadeClassifier(cascade)

Name = str(input("Enter your Name : "))
Roll_Number = int(input("Enter your Roll_Number : "))
dataset = 'dataset'
sub_data = Name
path = os.path.join(dataset, sub_data)

if not os.path.isdir(path):
os.mkdir(path)
print(sub_data)

info = [str(Name), str(Roll_Number)]
with open('student.csv', 'a') as csvFile:
write = csv.writer(csvFile)
write.writerow(info)
csvFile.close()

print("Starting video stream...")
cam = cv2.VideoCapture(1)
time.sleep(2.0)
total = 0

while total < 50:
print(total)
_, frame = cam.read()
img = imutils.resize(frame, width=400)
rects = detector.detectMultiScale(
cv2.cvtColor(img, cv2.COLOR_BGR2GRAY), scaleFactor=1.1,
minNeighbors=5, minSize=(30, 30))

for (x, y, w, h) in rects:
    cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)
    p = os.path.sep.join([path, "{}.png".format(
        str(total).zfill(5))])
    cv2.imwrite(p, img)
    total += 1

cv2.imshow("Frame", frame)
key = cv2.waitKey(1) & 0xFF
if key == ord("q"):
    break

cam.release()
cv2.destroyAllWindows()

[msavinash]

Please share more details about the issue and how to reproduce the error.