TypeError: 'NoneType' object is not iterable

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Hello world, I am trying to activate a github code that uses OpenCV, and I got an error of a NoneType, Please I will appreciate any help !!!!

github link: https://github.com/DevashishPrasad/Sm...

* There is nothing wrong with the import of the file, I used the debugger and the problem might be with the cv2.threshold function.

PLEASE HELP!!

code:

from __future__ import division
import numpy as np
import cv2
import imutils


font = cv2.FONT_HERSHEY_SIMPLEX


ys = 140
ye = 480
xs = 160
xe = 480



def distMap(frame1, frame2):
    frame1_32 = np.float32(frame1)
    frame2_32 = np.float32(frame2)
    diff32 = frame1_32 - frame2_32
    norm32 = np.sqrt(diff32[:, :, 0] ** 2 + diff32[:, :, 1] ** 2 + diff32[:, :, 2] ** 2) / np.sqrt(
        255 ** 2 + 255 ** 2 + 255 ** 2)
    dist = np.uint8(norm32 * 255)
    return dist



cap = cv2.VideoCapture('video.mp4')

_, frame1 = cap.read()
frame1 = cv2.resize(frame1, (640, 480))
frame1 = frame1[ys:ye, xs:xe]


_, frame2 = cap.read()
frame2 = cv2.resize(frame2, (640, 480))
frame2 = frame2[ys:ye, xs:xe]

while (True):
    ret, frame3 = cap.read()
    frame3 = cv2.resize(frame3, (640, 480))

    frame3 = frame3[ys:ye, xs:xe]
    frame4 = frame3.copy()

    dist = distMap(frame1, frame3)

    frame1 = frame2
    frame2 = frame3


    blur = cv2.GaussianBlur(dist, (11, 11), 0)


    thresh = cv2.threshold(blur, 25, 255, cv2.THRESH_BINARY)[1]
    thresh = cv2.dilate(thresh, None, iterations=1)

    cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
                            cv2.CHAIN_APPROX_SIMPLE)
    mask = np.ones(thresh.shape[:2], dtype="uint8") * 255

    cnts = cnts[0] if imutils.is_cv2() else cnts[1]



    for c in cnts:

        if cv2.contourArea(c) < 200:
            cv2.drawContours(mask, [c], -1, 0, -1)
            continue


    thresh = cv2.bitwise_and(thresh, thresh, mask=mask)

    temp = cv2.imread("temp")
    temp = cv2.resize(temp, (xe - xs, ye - ys))

    temp = cv2.bitwise_and(temp, temp, mask=thresh)

    weighted = cv2.addWeighted(frame4, 0.6, temp, 0.4, 0)

    load = round((cv2.countNonZero(thresh) / ((480 - 140) * (480 - 160))), 4) * 100


    cv2.imshow('weight', weighted)
    cv2.imshow('dist', thresh)
    cv2.imshow('blur', blur)
    cv2.putText(frame4, "LOAD = " + str(load) + "%", (30, 40), cv2.FONT_HERSHEY_SIMPLEX, 1.2, (0, 0, 255), 3)
    cv2.imshow('frame', frame4)
    if cv2.waitKey(1) & 0xFF == 27:
        break

cap.release()
cv2.destroyAllWindows()