cv2 assertion failure in windows

[pankaj-giri]

Environment -
tensorflow==1.15
keras==2.31
cv2==4.2.0

C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\keras\engine\saving.py:384: UserWarning: Error in loading the saved optimizer state. As a result, your model is starting with a freshly initialized optimizer.
warnings.warn('Error in loading the saved optimizer '
[2020-09-06 18:41:08,267] ERROR in app: Exception on /predict_input [POST]
Traceback (most recent call last):
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask\app.py", line 2447, in wsgi_app
response = self.full_dispatch_request()
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask\app.py", line 1952, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask_cors\extension.py", line 165, in wrapped_function
return cors_after_request(app.make_response(f(*args, **kwargs)))
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask\app.py", line 1821, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask_compat.py", line 39, in reraise
raise value
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask\app.py", line 1950, in full_dispatch_request
rv = self.dispatch_request()
File "C:\Users\girip\anaconda3\envs\python3.6\lib\site-packages\flask\app.py", line 1936, in dispatch_request
return self.view_functionsrule.endpoint
File "MNIST_web.py", line 138, in predict_input
predictions = segment_predict_digits(opencv_image)
File "MNIST_web.py", line 109, in segment_predict_digits
if cv2.contourArea(contour) < 100:
cv2.error: OpenCV(4.2.0) C:\projects\opencv-python\opencv\modules\imgproc\src\shapedescr.cpp:315: error: (-215:Assertion failed) npoints >= 0 && (depth == CV_32F || depth == CV_32S) in function 'cv::contourArea'