When doing a subrequest lookup, do not lookup using the quickhandler if

next_filter is NULL, since this implies that the subrequest will be
internal_fast_redirect'ed or will never be called. See line request.c:1513
onwards (in make_sub_request) also.  


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@291914 13f79535-47bb-0310-9956-ffa450edef68