Don't include events without a start time in iCal export (fixes #1625)

changelog/64_UNRELEASED_xxxx.xx.xx.md

@@ -1,6 +1,7 @@
 - Fixed that the "Add all list items to stock" shopping list workflow did not work for more than ~6 items (thanks @tjhowse)
 - Fixed that plural form handling (e.g. for quantity units) was wrong for negative numbers
 - Fixed that the context menu entries Consume and Transfer on the stock overview page were disabled when the amount in stock was < 1
+- Fixed that when there was any chore with a schedule, but without a "next estimated tracking" date/time, the iCal export was broken
 - The product and chore edit pages now have bottom-sticky save buttons
 - A product picture can now be added when creating a product (was currently only possible when editing a product)
 

controllers/CalendarApiController.php

@@ -21,6 +21,11 @@ class CalendarApiController extends BaseApiController
 			$vCalendar = new Calendar();
 			foreach ($events as $event)
 			{
+				if (!isset($event['start']))
+				{
+					continue;
+				}
+
 				$description = '';
 				if (isset($event['description']))
 				{