Using move setter for config file

main.cpp

@@ -181,7 +181,7 @@ int main(int argc, const char * argv[]) {
             std::cerr << "screensaver: reading config file " << config_path << '\n';
             nlohmann::json j;
             config_file >> j;
-            main_saver->config(j);
+            main_saver->config(std::move(j));
         }
 
         sc::gui::app().fps(main_saver->fps());