[_391] Add missing return to set_log_level(...)

This prevents a past the end iterator dereference.

core/src/main.cpp

@@ -679,6 +679,7 @@ auto set_log_level(const json& _config) -> void
 
 	if (iter == std::end(_config)) {
 		spdlog::set_level(spdlog::level::info);
+		return;
 	}
 
 	const auto& lvl_string = iter->get_ref<const std::string&>();