fix: ensure schedule.last_date is not None before comparison

program/services.py

@@ -535,7 +535,7 @@ def generate_timeslots(schedule: Schedule) -> list[TimeSlot]:
                 starts[k] = starts[k] + relativedelta(days=+schedule.add_days_no)
                 ends[k] = ends[k] + relativedelta(days=+schedule.add_days_no)
 
-            if ends[k].date() > schedule.last_date:
+            if schedule.last_date and ends[k].date() > schedule.last_date:
                 schedule.last_date = ends[k].date()
         timeslots.append(
             TimeSlot(