Temporarily revert r1537556.

* subversion/mod_dav_svn/mod_dav_svn.c
  (dav_svn__translate_name): Don't use SVN_VA_NULL to allow some changes
    I'm about to make to be backported.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1537693 13f79535-47bb-0310-9956-ffa450edef68