ra_serf: Pass log test #5 ('svn log -v -r 1:0 wc_root').
ra_serf: Pass log test #5 ('svn log -v -r 1:0 wc_root').

* subversion/libsvn_ra_serf/xml.c
  (add_tag_buckets): Properly handle an empty value.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@859101 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion