message: Added unit test for empty dictionaries.
diff: @@ -52,6 +52,12 @@ mod tests {
  }
  }
  + #[test]
  + fn test_empty_term_dictionary() {
  + let empty = TermDictionary::empty();
  + assert!(empty.stream().next().is_none());
  + }
  +
  #[test]
  fn test_term_ordinals() {
  const COUNTRIES: [&'static str; 7] = [
  