Remove bogus error message when a redirect doesn't set Location.

Instead, use an empty string to avoid coredump if the error message
was supposed to include a location but doesn't.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@83675 13f79535-47bb-0310-9956-ffa450edef68