Validate previous tx outputs for get_psbt_input

[notmandatory]

"In get_psbt_input, the size of the previous transaction's output vector is similarly assumed, which could lead to a crash when creating a transaction."

[ItshMoh]

Hey @notmandatory I have tried to fix the issue by checking the size of prev_tx.output vector. I have implemented in this way.

if let Some(prev_tx) = self.indexed_graph.graph().get_tx(prev_output.txid) {
            if (prev_output.vout as usize) < prev_tx.output.len() {
                if desc.is_witness() || desc.is_taproot() {
                    psbt_input.witness_utxo =
                        Some(prev_tx.output[prev_output.vout as usize].clone());
                }
                if !desc.is_taproot() && (!desc.is_witness() || !only_witness_utxo) {
                    psbt_input.non_witness_utxo = Some(prev_tx.as_ref().clone());
                }
            } else {
                // Handle the out-of-bounds case by returning an appropriate error
                return Err(CreateTxError::InvalidVoutIndex(prev_output));
            }
        }

I have made a PR resolving this issue. Here is the PR(bitcoindevkit/bdk#1911).