add collateral only when using plutus (#3)

* add collateral only when using plutus

* update check isUsingPlutus

---------

Co-authored-by: tony <[email protected]>

Author: baymac

packages/translucent/src/translucent/tx.ts

@@ -840,8 +840,8 @@ export class Tx {
       );
     }
     this.txBuilder.select_utxos(2);
-
-    {
+    const isUsingPlutus = Object.keys(this.scripts).length > 0;
+    if (isUsingPlutus) {
       let foundUtxo = walletUTxOs.find(
         (x) =>
           BigInt(x.output().amount().coin().to_str()) >=