Change lines 146-155 from this:

  if ((cli_name(cptr))[0] && cli_cookie(cptr) == COOKIE_VERIFIED) {
    /*
     * NICK and PONG already received, now we have USER...
     */
    return register_user(cptr, sptr, cli_name(sptr), username);
  }
  else {
    ircd_strncpy(user->username, username, USERLEN);
    ircd_strncpy(user->host, cli_sockhost(cptr), HOSTLEN);
  }

To this:

  ircd_strncpy(user->username, username, USERLEN);
  ircd_strncpy(user->host, cli_sockhost(cptr), HOSTLEN);

  if ((cli_name(cptr))[0] && cli_cookie(cptr) == COOKIE_VERIFIED) {
    /*
     * NICK and PONG already received, now we have USER...
     */
    return register_user(cptr, sptr, cli_name(sptr), username);
  }