message: improve code readability: duplicate local var of child
  Closes:
  Approved by: huitseeker
diff: @@ -112,10 +112,10 @@ impl WalletLibrary {
  pub fn new_address(&mut self) -> Result<(AccountAddress, ChildNumber)> {
  let child = self.key_factory.private_child(self.key_leaf)?;
  let address = child.get_address()?;
  - let child = self.key_leaf;
  + let old_key_leaf = self.key_leaf;
  self.key_leaf.increment();
  - if self.addr_map.insert(address, child).is_none() {
  - Ok((address, child))
  + if self.addr_map.insert(address, old_key_leaf).is_none() {
  + Ok((address, old_key_leaf))
  } else {
  Err(WalletError::LibraWalletGeneric(
  "This address is already in your wallet".to_string(),
  