impoly crop frames from a webcam

I am getting an error when I try to crop a polygon area from a webcam video (which only shows the cropped polygon from the frame)

vid=videoinput('macvideo',1,'YCbCr422_1280x720');
set(vid,'FramesPerTrigger',Inf);
set(vid,'ReturnedColorspace','rgb');
vid.FrameGrabInterval=5;
 
start(vid);
data=getsnapshot(vid);
imshow(data);
h = impoly();
position = wait(h);
BW = createMask(h);

while(vid.FramesAcquired<=100)
    data=getsnapshot(vid);
    data(~BW) = 255;
    imshow(data);
end
stop(vid);
flushdata(vid);
clear all;

When I run this script, I see a snapshot of my webcam where I can draw a polygon on it. But that is it. When I close the image after setting a polygon, it gives me an error

Invalid or deleted object.

Error in imroi/parseInputsForCreateMask (line

90)

h_ax = ancestor(obj.h_group,'axes');

Error in imroi/createMask (line 258)

[obj,h_im] =

parseInputsForCreateMask(varargin{:});

Error in camshift2 (line 11)

BW = createMask(h);