Drop the unnecessary UTXO based on the UTXOs present, not on earlier wallet things

Instead of dropping the unnecessary UTXO based on whether the wallet did something,
do it based on whether two UTXOs are there.

src/wallet/rpcwallet.cpp

@@ -4525,8 +4525,8 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const C
             complete &= SignPSBTInput(PublicOnlySigningProvider(pwallet), *psbtx.tx, input, sigdata, i, sighash_type);
         }
 
-        if (it != pwallet->mapWallet.end()) {
+        // If both UTXO types are present, drop the unnecessary one.
-            // Drop the unnecessary UTXO if we added both from the wallet.
+        if (input.non_witness_utxo && !input.witness_utxo.IsNull()) {
             if (sigdata.witness) {
                 input.non_witness_utxo = nullptr;
             } else {