findEllipses exception

[dmaritex]

System Information

version: 4.11.0
OS: Win11

Detailed description

An exception is raised when performing:
cv::ximgproc::findEllipses
it seems that tries to access a pixel out of range on an intermediate image in find_ellipses.cpp EllipseDetectorImpl::preProcessing

lines 1302
for (int i = 0; i <= imgSize.height; i++) {
int *tmpMag = magBuffer[(i > 0) + 1] + 1;
const short *tmpDx = dx.ptr(i);

In debug mode it seems to crash directly on the first inspected image. In release surprisingly it can run for a while, but still crashes randomly while labelling ellipses

Steps to reproduce

#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/calib3d.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/ximgproc.hpp>

    cv::Mat ellipses;
    cv::ximgproc::findEllipses(frameGray, ellipses);

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues, forum.opencv.org, Stack Overflow, etc and have not found any solution
• I updated to the latest OpenCV version and the issue is still there
• There is reproducer code and related data files (videos, images, onnx, etc)