message: add check to proptest
diff: @@ -1617,6 +1617,7 @@ mod tests {
  // multivalue fast field tests
  for segment_reader in searcher.segment_readers().iter() {
  + let id_reader = segment_reader.fast_fields().u64(id_field).unwrap();
  let ff_reader = segment_reader.fast_fields().u64s(multi_numbers).unwrap();
  let bool_ff_reader = segment_reader.fast_fields().bools(multi_bools).unwrap();
  for doc in segment_reader.doc_ids_alive() {
  @@ -1624,6 +1625,7 @@ mod tests {
  ff_reader.get_vals(doc, &mut vals);
  assert_eq!(vals.len(), 2);
  assert_eq!(vals[0], vals[1]);
  + assert_eq!(id_reader.get_val(doc as u64), vals[0]);
  let mut bool_vals = vec![];
  bool_ff_reader.get_vals(doc, &mut bool_vals);
  