getline() fixes...

If ap_get_brigade() returns APR_SUCCESS but an empty brigade, bail out.
Previously, we kept going and sometimes segfaulted while operating on
what we thought was the first bucket.

Free the temporary brigade used by getline().


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86581 13f79535-47bb-0310-9956-ffa450edef68