Fix: Assertion failure in DelayedPhotoLoader (Fixes: #404)

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Fix: When setting CardDAV addressbooks for collected recipients/senders from the admin configuration, setting them as
   `dont_override` is a mandatory action for the admin, otherwise the setting might get overridden by user preferences in
   conjunction with the use of other plugins (that are completely unrelated to these addressbooks). (Fixes #391)
+- Fix: Assertion failure in DelayedPhotoLoader (Fixes: #404)
 
 ## Version 4.4.3 (to 4.4.2)
 

src/DelayedPhotoLoader.php

@@ -240,8 +240,12 @@ private function storeToRoundcubeCache(string $photoData, VObject\Property $phot
     private function determineCacheKey(): string
     {
         $uid = (string) $this->vcard->UID;
-        $userid = $_SESSION['user_id'];
-        assert(is_string($userid), "user must be logged on to use photo cache");
+
+        if (!isset($_SESSION['user_id'])) {
+            throw new \Exception("determineCacheKey: user must be logged on to use photo cache");
+        }
+
+        $userid = (string) $_SESSION['user_id'];
 
         $key  = "photo_";
         $key .= $userid . "_" ;