ts: Fix empty instructions array (#877)

ts/src/program/namespace/transaction.ts

@@ -16,9 +16,7 @@ export default class TransactionFactory {
     const txFn: TransactionFn<IDL, I> = (...args): Transaction => {
       const [, ctx] = splitArgsAndCtx(idlIx, [...args]);
       const tx = new Transaction();
-      if (ctx.instructions !== undefined) {
-        tx.add(...ctx.instructions);
-      }
+      ctx.instructions?.forEach((ix) => tx.add(ix));
       tx.add(ixFn(...args));
       return tx;
     };