Follow up r1673004, fix segfault when cert has no hostnames.
Follow up r1673004, fix segfault when cert has no hostnames.

* subversion/svn/auth-cmd.c
  (match_certificate): hostnames can be NULL if the cert doesn't have
    a CN that looks like a hostname and has no Subject Alt Names.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1673063 13f79535-47bb-0310-9956-ffa450edef68

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