message: Fix build with logging disabled
diff: @@ -236,7 +236,11 @@ logger::~logger() {
  logger::logger(actor_system& sys)
  : system_(sys),
  +#ifdef CAF_LOG_LEVEL
  level_(CAF_LOG_LEVEL),
  +#else
  + level_(0),
  +#endif
  flags_(0),
  queue_(policy{}) {
  // nop
  