Fix a segfault in kidney blame.
Fix a segfault in kidney blame.

* subversion/libsvn_ra/util.c
  (svn_ra__assert_capable_server): Handle NULL paths.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1498455 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion