Bug-fix: segfault in dco_get_peer_stats()

Bug-fix: segfault in dco_get_peer_stats()

  We persist peer-stats when restarting, but an early restart
  before open_tun results in a segfault in dco_get_peer_stats().
  To reproduce, trigger a TLS handshake error due to lack of common
  protocols, for example.

  Fix by checking  that tuntap is defined before dereferencing it.

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Antonio Quartulli <a@unstable.cc>
Message-Id: <20230327171236.51771-1-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26530.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>