message: fix: cli subcommand setting
diff: @@ -88,7 +88,7 @@ fn arg_private_key() -> Arg<'static, 'static> {
  fn cli() -> App<'static, 'static> {
  SubCommand::with_name("cli")
  .about("Running ckb cli")
  - .setting(AppSettings::ArgRequiredElseHelp)
  + .setting(AppSettings::SubcommandRequiredElseHelp)
  .subcommand(
  SubCommand::with_name("sign")
  .about("Sign transaction using sha3-secp256k1 defined in system cell")
  