Empty rendered image: TypeError: 'NoneType' object is not subscriptable

Question

Empty rendered image: TypeError: 'NoneType' object is not subscriptable

I am trying the render the image which uses blender-python. But the rendered image does not contain any information(None). I could not find the reason.

Here is the reference to the code where the rendered image is read and found to be None. Thus it throws the following error

File "./blender_hands.py", line 224, in run
    segm_img = cv2.imread(tmp_segm_path)[:, :, 0]
TypeError: 'NoneType' object is not subscriptable

Any suggestions solve this error would be very helpful, thank you!