Recognize absencereason as nullable

aleksis/apps/alsijil/frontend/components/coursebook/absences/ManageStudentsDialog.vue

@@ -116,7 +116,7 @@ export default {
             participationStatus.isOptimistic = newStatus.isOptimistic;
           });
 
-          this.markAsAbsentDay.reason = incomingStatuses[0].absenceReason.name;
+          this.markAsAbsentDay.reason = incomingStatuses[0].absenceReason?.name;
           this.markAsAbsentDay.num = incomingStatuses.length;
 
           return storedDocumentations;