message: das.cli: clarify control flow
diff: @@ -449,7 +449,7 @@ namespace elle
  ELLE_TRACE("convert: %s", this);
  if (this->_flag)
  throw ValuelessOption(this->_option);
  - if (this->_values.empty())
  + else if (this->_values.empty())
  {
  if (this->_positional)
  {
  