svnrdump <unknown_command> url_to_valid_repo causes segfault
svnrdump <unknown_command> url_to_valid_repo causes segfault

* subversion/svnrdump/svnrdump.c
  (main): handle the error cases when unknown_command is given and *no*
   subcommand given.

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