From 88f76e4bc114be40b29b834debb104ae8f8d810d Mon Sep 17 00:00:00 2001
From: Ralf Becker <RalfBecker@outdoor-training.de>
Date: Fri, 8 Oct 2021 14:58:27 +0200
Subject: [PATCH] fix PHP 8.0 error: array_keys(): Argument #1 ($array) must be
 of type array, null given

---
 calendar/inc/class.calendar_boupdate.inc.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/calendar/inc/class.calendar_boupdate.inc.php b/calendar/inc/class.calendar_boupdate.inc.php
index 81f43a6811..b64b0cd269 100644
--- a/calendar/inc/class.calendar_boupdate.inc.php
+++ b/calendar/inc/class.calendar_boupdate.inc.php
@@ -1634,7 +1634,7 @@ class calendar_boupdate extends calendar_bo
 			$memberships = $GLOBALS['egw']->accounts->memberships($uid,true);
 		}
 		$memberships[] = $uid;
-		return array_intersect($memberships, array_keys($event['participants'])) && $this->check_perms(Acl::EDIT,0,$uid);
+		return array_intersect($memberships, array_keys($event['participants'] ?? [])) && $this->check_perms(Acl::EDIT,0,$uid);
 	}
 
 	/**