From 3534ed9040c837d295964d38258ad472881f052c Mon Sep 17 00:00:00 2001
From: Ralf Becker <RalfBecker@outdoor-training.de>
Date: Wed, 10 Nov 2021 13:00:59 +0100
Subject: [PATCH] fix PHP 8.0 TypeError: calendar_tracking::track(): Argument
 #1 ($data) must be of type array, null given

---
 calendar/inc/class.calendar_boupdate.inc.php | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/calendar/inc/class.calendar_boupdate.inc.php b/calendar/inc/class.calendar_boupdate.inc.php
index 320c409d28..fb664d3426 100644
--- a/calendar/inc/class.calendar_boupdate.inc.php
+++ b/calendar/inc/class.calendar_boupdate.inc.php
@@ -1829,12 +1829,13 @@ class calendar_boupdate extends calendar_bo
 			}
 
 			// Update history
-			$event = $this->read($cal_id, $recur_date, $ignore_acl, 'server');
-			$tracking = new calendar_tracking($this);
-			$tracking->track($event, $old_event);
-
+			if (($event = $this->read($cal_id, $recur_date, $ignore_acl, 'server')))
+			{
+				$tracking = new calendar_tracking($this);
+				$tracking->track($event, $old_event);
+			}
 			// notify the link-class about the update, as other apps may be subscribed to it
-			Link::notify_update('calendar',$event['id'],$event,"update");
+			Link::notify_update('calendar', $cal_id, $event, "update");
 		}
 		return $Ok;
 	}