mod_ssl: Fix quick renegotiation (OptRenegotiaton) with no intermediate

in the client certificate chain.  PR 55786.

This is done by handling an empty cert chain as no/NULL chain.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1756542 13f79535-47bb-0310-9956-ffa450edef68