message: Create a BlockBuilder even if validators are unknown
diff: @@ -115,26 +115,21 @@ impl BlockSynchronizer {
  }
  Entry::Vacant(entry) => {
  let era_id = request.era_id;
  - let validator_matrix = {
  - let era_validators = match self.validators.get(&era_id) {
  + let mut validator_matrix = ValidatorMatrix::new(self.fault_tolerance_fraction);
  + match self.validators.get(&era_id) {
  None => {
  debug!(
  era_id = %era_id,
  "missing validators for given era"
  );
  - return Effects::new();
  }
  - Some(validators) => validators.clone(),
  - };
  - let mut validator_matrix = ValidatorMatrix::new(self.fault_tolerance_fraction);
  - validator_matrix.register_era(era_id, era_validators);
  - Rc::new(validator_matrix)
  + Some(validators) => validator_matrix.register_era(era_id, validators.clone()),
  };
  entry.insert(BlockBuilder::new(
  request.block_hash,
  era_id,
  - validator_matrix,
  + Rc::new(validator_matrix),
  request.should_fetch_execution_state,
  ));
  }
  