Merge #1790: fix(wallet): improve safety on finaize psbt

e8a9638 fix(wallet): improve safety on finaize psbt (f3r10)

Pull request description:

  <!-- You can erase any parts of this template not applicable to your Pull Request. -->
  fix #1711
  ### Description

  This PR replaces how currently potentially bug-prone PSBT's input access is done using a more carefully approach.

  ### Notes to the reviewers

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  of the PR were done in a specific way -->

  ### Changelog notice

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  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  rustaceanrob:
    ACK e8a9638
  evanlinjin:
    ACK e8a9638

Tree-SHA512: ad25a9d5d47cbdc41b11ea4ce57b30c6855ea391c0f053dffbee0c3dd1b06c6b227e056ede69eee6026e8b72915fe06c366d0a4e2fd6a1d454fc8dafed80b74a

crates/wallet/src/wallet/mod.rs

@@ -1901,8 +1901,11 @@ impl Wallet {
                         Ok(_) => {
                             // Set the UTXO fields, final script_sig and witness
                             // and clear everything else.
-                            let original = mem::take(&mut psbt.inputs[n]);
-                            let psbt_input = &mut psbt.inputs[n];
+                            let psbt_input = psbt
+                                .inputs
+                                .get_mut(n)
+                                .ok_or(SignerError::InputIndexOutOfRange)?;
+                            let original = mem::take(psbt_input);
                             psbt_input.non_witness_utxo = original.non_witness_utxo;
                             psbt_input.witness_utxo = original.witness_utxo;
                             if !tmp_input.script_sig.is_empty() {