diff --git a/calendar/js/et2_widget_daycol.ts b/calendar/js/et2_widget_daycol.ts
index 3e5eb26942..ec31040895 100644
--- a/calendar/js/et2_widget_daycol.ts
+++ b/calendar/js/et2_widget_daycol.ts
@@ -380,7 +380,11 @@ export class et2_calendar_daycol extends et2_valueWidget implements et2_IDetache
 		{
 			let event : any = egw.dataGetUIDdata('calendar::' + event_ids[i]);
 			event = event && event.data || false;
-			waitForGroups.push((<CalendarApp>app.calendar)._fetch_group_members(event).then(() =>
+			if(!event)
+			{
+				continue;
+			}
+			waitForGroups.push(((<CalendarApp>this.getInstanceManager().app_obj.calendar)._fetch_group_members(event)).then(() =>
 			{
 				if(event && event.date && et2_calendar_event.owner_check(event, this) && (
 					event.date === this.options.date ||
diff --git a/calendar/js/et2_widget_planner.ts b/calendar/js/et2_widget_planner.ts
index c3d7d3c2a8..bfc174d7b0 100644
--- a/calendar/js/et2_widget_planner.ts
+++ b/calendar/js/et2_widget_planner.ts
@@ -1916,7 +1916,11 @@ export class et2_calendar_planner extends et2_calendar_view implements et2_IDeta
 			{
 				for(var i = 0; i < data.length; i++)
 				{
-					var event = egw.dataGetUIDdata('calendar::' + data[i]);
+					let event = egw.dataGetUIDdata('calendar::' + data[i]);
+					if(!event || !event.data)
+					{
+						continue;
+					}
 
 					waitForGroups.push((<CalendarApp>app.calendar)._fetch_group_members(event.data));
 				}