protected function mergeDefaults(array $defaults, $level = '')
    {
        foreach ($defaults as $key => $value) {
            if (is_array($value)) {
                $original = $this->getIfExists(ltrim("$level.$key", "."));
                if (is_array($original)) {
                    $this->mergeDefaults($value, "$level.$key");
                } elseif ($original instanceof NoItemFoundMessage) {
                    $this->set(ltrim("$level.$key", "."), $value);
                }
            } else {
                if (!$this->exists(ltrim("$level.$key", "."))) {
                    $this->set(ltrim("$level.$key", "."), $value);
                }
            }
        }
    }