Issue #3204015: Replace Toolbar BackboneJS usage with VanillaJS equivalent

core/modules/migrate/src/Plugin/migrate/process/Download.php

@@ -155,6 +155,10 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       throw new MigrateException("{$e->getMessage()} ($source)");
     }
 
+    if (is_resource($destination_stream)) {
+      fclose($destination_stream);
+    }
+
     return $final_destination;
   }