Fix a potential segfault.
Fix a potential segfault.

* subversion/libsvn_wc/log.h
  (SVN_WC__FLUSH_LOG_ACCUM): Don't attempt to flush a NULL log_accum.

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