Ticket #7092: patch

algorithm.

@@ -735 +735 @@
         return std::for_each(img.begin().x(), img.end().x(), fun);
     } else {
         for (std::ptrdiff_t y=0; y<img.height(); ++y)
-            fun = std::for_each(img.row_begin(y),img.row_end(y),fun);
-        return fun;
+            std::for_each(img.row_begin(y),img.row_end(y),fun);
+        return std::move(fun);
     }
 }