ra_serf: Close the dirs and editor batons; don't pass 0-length textdeltas.
ra_serf: Close the dirs and editor batons; don't pass 0-length textdeltas.

(We can now do a single-directory checkout without problems.)

* subversion/libsvn_ra_serf/serf.c
  (report_context_t): Add dir_baton field.
  (handle_fetch): Call textdelta() only if we have data (otherwise, it'll SEGV)
  (start_report): Update the directory baton pointer when we fetch it
  (finish_report): Close the directory and editor when we're done.

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