message: catch user misuse error case
diff: @@ -235,6 +235,8 @@ void wamp_router::check_has_closed()
  std::future<uverr> wamp_router::listen(auth_provider auth,
  const listen_options& options)
  {
  + if (options.use_ssl && m_kernel->get_ssl() == nullptr)
  + throw std::runtime_error("wampcc kernel SSL context is null; can't use SSL");
  auto on_new_client = [this, auth](std::unique_ptr<tcp_socket> sock) {
  /* IO thread */
  @@ -304,6 +306,7 @@ std::future<uverr> wamp_router::listen(auth_provider auth,
  };
  /* Create the actual IO server socket */
  +
  std::unique_ptr<tcp_socket> sock(options.use_ssl ? new ssl_socket(m_kernel)
  : new tcp_socket(m_kernel));
  