Merge r1328950:

Fix segfault in logging if r->useragent_addr or c->client_addr is unset.

Reviewed by: sf, jorton, trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1334344 13f79535-47bb-0310-9956-ffa450edef68