Merge pull request #21067 An error occurred from NickJackolson:nickjackolson/imread-warning

modules/imgcodecs/src/loadsave.cpp

@@ -226,8 +226,10 @@ static ImageDecoder findDecoder( const String& filename ) {
     FILE* f= fopen( filename.c_str(), "rb" );
 
     /// in the event of a failure, return an empty image decoder
-    if( !f )
+    if( !f ) {
+        CV_LOG_WARNING(NULL, "imread_('" << filename << "'): can't open/read file: check file path/integrity");
         return ImageDecoder();
+    }
 
     // read the file signature
     String signature(maxlen, ' ');

modules/photo/src/seamless_cloning.cpp

@@ -67,6 +67,7 @@ static Mat checkMask(InputArray _mask, Size size)
 void cv::seamlessClone(InputArray _src, InputArray _dst, InputArray _mask, Point p, OutputArray _blend, int flags)
 {
     CV_INSTRUMENT_REGION();
+    CV_Assert(!_src.empty());
 
     const Mat src  = _src.getMat();
     const Mat dest = _dst.getMat();