message: [types] use default for missing ledger_consistency_proof
  Closes:
  Approved by: mimoo
diff: @@ -132,7 +132,7 @@ impl<Sig: Signature> TryFrom<crate::proto::types::UpdateToLatestLedgerResponse>
  .collect::<Result<Vec<_>>>()?;
  let ledger_info_with_sigs = proto
  .ledger_info_with_sigs
  - .ok_or_else(|| format_err!("Missing ledger_info_with_sigs"))?
  + .unwrap_or_else(Default::default)
  .try_into()?;
  let validator_change_events = proto
  .validator_change_events
  @@ -141,7 +141,7 @@ impl<Sig: Signature> TryFrom<crate::proto::types::UpdateToLatestLedgerResponse>
  .collect::<Result<Vec<_>>>()?;
  let ledger_consistency_proof = proto
  .ledger_consistency_proof
  - .ok_or_else(|| format_err!("Missing ledger_consistency_proof"))?
  + .unwrap_or_else(Default::default)
  .try_into()?;
  Ok(Self {
  