message: Add iter::sum test for empty list of Decimals
diff: @@ -1162,7 +1162,10 @@ mod tests {
  assert_eq!(
  items.into_iter().sum::<Decimal>(),
  Decimal(Uint128::from(4u128))
  - )
  + );
  +
  + let empty: Vec<Decimal> = vec![];
  + assert_eq!(Decimal::zero(), empty.iter().sum())
  }
  #[test]
  