Add warning if tile is missing / can not be decoded.

Author: fancycode

libheif/image-items/grid.cc

@@ -468,6 +468,10 @@ Error ImageItem_Grid::decode_and_paste_tile_image(heif_item_id tileID, uint32_t
 
   auto tileItem = get_context()->get_image(tileID, true);
   if (!tileItem && !options.strict_decoding) {
+    inout_image->add_warning(Error{
+      heif_error_Invalid_input,
+      heif_suberror_Missing_grid_images,
+    });
     // We ignore missing images.
     return progress_and_return_ok(options, progress_counter);
   }
@@ -481,6 +485,10 @@ Error ImageItem_Grid::decode_and_paste_tile_image(heif_item_id tileID, uint32_t
   if (!decodeResult) {
     if (!options.strict_decoding) {
       // We ignore broken tiles.
+      inout_image->add_warning(Error{
+        heif_error_Invalid_input,
+        heif_suberror_Missing_grid_images,
+      });
       return progress_and_return_ok(options, progress_counter);
     }