fix: nitpicking

program/services.py

@@ -849,7 +849,7 @@ def get_timerange_timeslot_entries(
     if not include_virtual:
         return [make_timeslot_entry(timeslot=timeslot) for timeslot in timeslots]
 
-    if timeslots is None:
+    if not timeslots:
         return []
 
     timeslot_entries = []