Make tls_ctx_restrict_ciphers accept NULL as char *cipher_list.

Make tls_ctx_restrict_ciphers accept NULL as char *cipher_list.

This adds some ifs to check for NULL in tls_ctx_restrict_ciphers() to
prepare
for disabling export ciphers by default in OpenVPN 2.4+.

Also let tls_ctx_restrict_ciphers always be called, also when *cipher_list
is
NULL.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <52C8922E.3030607@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8173
Signed-off-by: Gert Doering <gert@greenie.muc.de>