Merge pull request #25945 from vrabaud:02_fix

Fix size() for 0d matrix #25945

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- [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/core/test/test_mat.cpp

@@ -2414,7 +2414,15 @@ TEST(Mat, regression_18473)
     EXPECT_EQ((int)5, (int)m.at<short>(19, 49, 99));
 }
 
-// FITIT: remove DISABLE_ when 1D Mat is supported
+TEST(Mat0D, basic)
+{
+    Mat1b m1, m2(0, nullptr);
+    ASSERT_EQ(0, m1.size().width);
+    ASSERT_EQ(0, m1.size().height);
+    ASSERT_EQ(1, m2.size().width);
+    ASSERT_EQ(1, m2.size().height);
+}
+
 TEST(Mat1D, basic)
 {
     std::vector<int> sizes { 100 };