Description
===========
Crash in community version of server with X plugin loaded when checking
for SSL system variables and using expired certificates.

Fix
===
Add validation if certificate is not null when checking for certificate
details.

RB: 16362
Reviewed by: Grzegorz Szwarc <grzegorz.szwarc@oracle.com>
Reviewed by: Lukasz Kotula <lukasz.kotula@oracle.com>