Eliminate core dumps when CacheRoot is not defined and ProxyRequests On.

This still allows proxy to operate. ProxyPass core dumps should be largely
if not totally eliminated. Also. minor cleanup in this section.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@77037 13f79535-47bb-0310-9956-ffa450edef68