Merge pull request #27418 from dkurt:fix_valgrind_warnings

Fix valgrind warnings in tests #27418

### Pull Request Readiness Checklist

https://pullrequest.opencv.org/buildbot/builders/4_x_valgrind-lin64-debug/builds/100131/steps/test_calib3d/logs/valgrind%20summary
https://pullrequest.opencv.org/buildbot/builders/4_x_valgrind-lin64-debug/builds/100131/steps/test_imgproc/logs/valgrind%20summary

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/imgproc/test/test_cornersubpix.cpp

@@ -69,6 +69,8 @@ TEST(Imgproc_CornerSubPix, out_of_image_corners)
 TEST(Imgproc_CornerSubPix, corners_on_the_edge)
 {
     cv::Mat image(500, 500, CV_8UC1);
+    RNG& rng = TS::ptr()->get_rng();
+    cvtest::randUni(rng, image, 0, 255);
     cv::Size win(1, 1);
     cv::Size zeroZone(-1, -1);
     cv::TermCriteria criteria;