Fixed: Calendar defaultProps for statistics

Fixes #534

frontend/src/Calendar/Agenda/AgendaEvent.js

@@ -133,4 +133,10 @@ AgendaEvent.propTypes = {
   longDateFormat: PropTypes.string.isRequired
 };
 
+AgendaEvent.defaultProps = {
+  statistics: {
+    percentOfTracks: 0
+  }
+};
+
 export default AgendaEvent;

frontend/src/Calendar/Events/CalendarEvent.js

@@ -134,4 +134,10 @@ CalendarEvent.propTypes = {
   onEventModalOpenToggle: PropTypes.func.isRequired
 };
 
+CalendarEvent.defaultProps = {
+  statistics: {
+    percentOfTracks: 0
+  }
+};
+
 export default CalendarEvent;