On the 2.4.x branch:

Merge of r1813767 from trunk.

mod_http2: avoid unnecessary data retrieval for a trace log. Allow certain
     information retrievals on null bucket beams where it makes sense.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1814420 13f79535-47bb-0310-9956-ffa450edef68