message: added assertion for empty vector
diff: @@ -375,6 +375,7 @@ mod batch_query_builder {
  assert!(n.consistency == Consistency::One);
  assert!(n.serial_consistency == None);
  assert!(n.timestamp == None);
  + assert!(n.queries.is_empty());
  }
  Err(_) => assert!(false,"Error should not happen"),
  }
  