Convert non-witness UTXOs to witness if witness sig created

If a witness signature was created when a non-witness UTXO is used,
convert the non-witness UTXO to a witness one.

src/script/sign.cpp

@@ -277,6 +277,11 @@ bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& t
     if (require_witness_sig && !sigdata.witness) return false;
     input.FromSignatureData(sigdata);
 
+    if (sigdata.witness) {
+        assert(!utxo.IsNull());
+        input.witness_utxo = utxo;
+    }
+
     // If both UTXO types are present, drop the unnecessary one.
     if (input.non_witness_utxo && !input.witness_utxo.IsNull()) {
         if (sigdata.witness) {