fix: handle empty payloads in scheduled task test page (#3316)

When parsePacket returns undefined for empty data (e.g. payload=''),
getScheduleTaskRunPayload crashes accessing .timezone on undefined.
Add a null guard that returns a failed SafeParse result so the run is
gracefully skipped by the existing filter(Boolean) logic.

Author: abhayjnayakk

apps/webapp/app/presenters/v3/TestTaskPresenter.server.ts

@@ -382,6 +382,11 @@ export class TestTaskPresenter {
 
 async function getScheduleTaskRunPayload(payload: string, payloadType: string) {
   const packet = await parsePacket({ data: payload, dataType: payloadType });
+
+  if (!packet) {
+    return { success: false as const, error: new Error("Empty payload") };
+  }
+
   if (!packet.timezone) {
     packet.timezone = "UTC";
   }