fix: set schedule of PlayoutEntry nullable

program/serializers.py

@@ -1301,7 +1301,7 @@ class NestedTimeslotSerializer(serializers.Serializer):
 
 class PlayoutEntrySerializer(serializers.Serializer):
     episode = serializers.SerializerMethodField()
-    schedule = serializers.SerializerMethodField()
+    schedule = serializers.SerializerMethodField(allow_null=True)
     show = serializers.SerializerMethodField()
     timeslot = NestedTimeslotSerializer()