Fix a segfault with mod_include when r->path_info is not set

(which is the case with mod_proxy).

My only question about this is whether we should place some value
(such as <UNKNOWN>) when path_info isn't set.

Submitted by:	Ian Holsman <ianh@cnet.com>
Reviewed by:	Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@90825 13f79535-47bb-0310-9956-ffa450edef68