Merge r1397172 from trunk:

"Iterate" directives: Report an error if no arguments are provided.

Submitted by: trawick
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1408742 13f79535-47bb-0310-9956-ffa450edef68