message: Fix clippy::len_zero
diff: @@ -600,7 +600,7 @@ impl AddAssign<u32> for BigUint {
  #[inline]
  fn add_assign(&mut self, other: u32) {
  if other != 0 {
  - if self.data.len() == 0 {
  + if self.data.is_empty() {
  self.data.push(0);
  }
  @@ -745,7 +745,7 @@ impl Sub<BigUint> for u32 {
  #[inline]
  fn sub(self, mut other: BigUint) -> BigUint {
  - if other.data.len() == 0 {
  + if other.data.is_empty() {
  other.data.push(self as BigDigit);
  } else {
  sub2rev(&[self as BigDigit], &mut other.data[..]);
  