
<!-- Describe the issue -->
Following commit 46004790588c24174a0bec49b540d158ce163ffd (@achow101), `decodepsbt` overstates the fee, apparently including both the `witness_utxo` and `non_witness_utxo` amounts in the inputs.

**Expected behavior**

The decoded fee should be the sum of the inputs, minus the sum of the outputs.

**Actual behavior**

The decoded fee is exactly twice the amount of the inputs, minus the sum of the outputs.

**To reproduce**

Build any PSBT using `createpsbt`, `walletprocesspsbt`, then decode it with `decodepsbt`. See the `fee` field in the JSON.

**System information**

I compiled myself from 5550fa5983ea59e7ccef6540b7ec49a1770fb3ca on Whonix 14.

Then I did `git revert 46004790588c24174a0bec49b540d158ce163ffd ` and the problem went away.

},
                RPCExamples{
                    HelpExampleCli("combinepsbt", R"('["mybase64_1", "mybase64_2", "mybase64_3"]')")
                },
            }.Check(request);
    RPCTypeCheck(request.params, {UniValue::VARR}, true);
    
    std::vector<PartiallySignedTransaction> psbtxs;
    UniValue txs = request.params[0].get_array();
    if (txs.empty()) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Parameter 'txs' cannot be empty");
    }
    for (unsigned int i = 0; i < txs.size(); ++i) {
        PartiallySignedTransaction psbtx;
        std::string error;
        if (!DecodeBase64PSBT(psbtx, txs[i].get_str(), error)) {
            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed %s", error));
        }
        psbtxs.push_back(psbtx);
    }
    PartiallySignedTransaction merged_psbt;
    const TransactionError error = CombinePSBTs(merged_psbt, psbtxs);
    if (error != TransactionError::OK) {
        throw JSONRPCTransactionError(error);
    }
    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
    ssTx << merged_psbt;
    return EncodeBase64((unsigned char*)ssTx.data(), ssTx.size());
}
UniValue finalizepsbt(const JSONRPCRequest& request)