Followup to r1350584: a missing sha1-checksum property can also be the empty string (e.g. <S:sha1-checksum/>)
Followup to r1350584: a missing sha1-checksum property can also be the
empty string (e.g. <S:sha1-checksum/>)

* subversion/libsvn_ra_serf/update.c:
  (try_get_wc_contents): look for both missing and empty string on the
    sha1-checksum property

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion