Update src/psbt.h file

Author: janus

src/psbt.h

@@ -1177,8 +1177,13 @@ struct PartiallySignedTransaction
             inputs.push_back(input);
 
             // Make sure the non-witness utxo matches the outpoint
-            if (input.non_witness_utxo && input.non_witness_utxo->GetHash() != tx->vin[i].prevout.hash) {
-                throw std::ios_base::failure("Non-witness UTXO does not match outpoint hash");
+            if (input.non_witness_utxo) {
+                if (input.non_witness_utxo->GetHash() != tx->vin[i].prevout.hash) {
+                    throw std::ios_base::failure("Non-witness UTXO does not match outpoint hash");
+                }
+                if (tx->vin[i].prevout.n >= input.non_witness_utxo->vout.size()) {
+                    throw std::ios_base::failure("Input specifies output index that does not exist");
+                }
             }
             ++i;
         }