Avoid assert in lapac.cpp if findHomography fails in BestOf2NearestMatcher::match

modules/core/src/lapack.cpp

@@ -878,6 +878,7 @@ double cv::determinant( InputArray _mat )
     size_t step = mat.step;
     const uchar* m = mat.data;
 
+    CV_Assert( !mat.empty() );
     CV_Assert( mat.rows == mat.cols && (type == CV_32F || type == CV_64F));
 
     #define Mf(y, x) ((float*)(m + y*step))[x]

modules/stitching/src/matchers.cpp

@@ -573,7 +573,7 @@ void BestOf2NearestMatcher::match(const ImageFeatures &features1, const ImageFea
 
     // Find pair-wise motion
     matches_info.H = findHomography(src_points, dst_points, matches_info.inliers_mask, CV_RANSAC);
-    if (std::abs(determinant(matches_info.H)) < std::numeric_limits<double>::epsilon())
+    if (matches_info.H.empty() || std::abs(determinant(matches_info.H)) < std::numeric_limits<double>::epsilon())
         return;
 
     // Find number of inliers