[nan-439] allow no output for script (#1797)

## Describe your changes
If an action has not output it would throw an error in the webapp

## Issue ticket number and link
NAN-439

## Checklist before requesting a review (skip if just adding/editing
APIs & templates)
- [ ] I added tests, otherwise the reason is: 
- [ ] I added observability, otherwise the reason is:
- [ ] I added analytics, otherwise the reason is:

packages/webapp/src/utils/utils.tsx

@@ -321,7 +321,10 @@ export const parseInput = (flow: Flow) => {
     return input;
 };
 
-export function generateResponseModel(models: NangoSyncModel[], output: string, isSync: boolean): Record<string, any> {
+export function generateResponseModel(models: NangoSyncModel[], output: string | undefined, isSync: boolean): Record<string, any> {
+    if (!output) {
+        return {};
+    }
     const model = models.find((model) => model.name === output);
     const jsonResponse = generateExampleValueForProperty(model as NangoSyncModel);
     if (!isSync) {