Add check for absence reason before creating absence in extend participation status mutation

aleksis/apps/alsijil/schema/participation_status.py

@@ -118,8 +118,8 @@ class ExtendParticipationStatusToAbsenceBatchMutation(graphene.Mutation):
 
             return participation, absence
 
-        else:
-            # No base absence, simply create one
+        elif participation.absence_reason:
+            # No base absence, simply create one if absence reason is given
             data = dict(
                 reason_id=participation.absence_reason.id,
                 person=participation.person,