message: Fix error for no hashes in consensus with cath up needed. Add comment about cloning of votes
diff: @@ -122,6 +122,8 @@ impl CatchupHandler {
  let votes: HashMap<(String, usize, Option<Vec<String>>), usize> = self.nodes_votes.iter().cloned()
  .filter_map(|e| e)
  .fold(HashMap::new(), |mut acc, vote| {
  + //WARN: It can be processed without excessive cloning two steps before, but then we will face double write borrowing.
  + //WARN: This is the most readable variant. However, not the most effective.
  let cnt = acc.get(&vote).unwrap_or(&0) + 1;
  acc.insert(vote, cnt);
  acc
  @@ -159,7 +161,7 @@ impl CatchupHandler {
  CommonError::InvalidStructure(
  "Can't parse target MerkleTree hash from nodes responses".to_string()))?;
  match hashes {
  - &None => (),
  + &None => {return Err(PoolError::from(CommonError::InvalidState("Empty consistency proof but catch up needed".to_string())));},
  &Some(ref hashes) => {
  match CatchupHandler::check_cons_proofs(&self.merkle_tree, hashes, &self.target_mt_root, self.target_mt_size) {
  Ok(_) => (),
  