Follow up commit to r26822.
Follow up commit to r26822.

Remove the api restriction of non-empty children_with_mergeinfo
instead ensure it programattically.

* subversion/libsvn_client/merge.c
  (drive_merge_report_editor): Ensure 'children_with_mergeinfo' is not empty
   before accessing its 0th element.

Suggested by: dlr

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