FIX #19031 TIME 0:10 Fixed warning for notification administration

src/app/notifications/controllers/NotificationsScheduleController.php

@@ -278,8 +278,8 @@ class NotificationsScheduleController
         }
 
         $configuration = ConfigurationModel::getByIdentifier(['identifier' => 'customization']);
-        $configuration = $configuration[0];
-        $configuration = json_decode($configuration['value'], true);
+        $configuration = $configuration[0] ?? null;
+        $configuration = json_decode($configuration['value'] ?? null, true);
 
         if (empty($configuration['schedulerPath']) || !is_file($configuration['schedulerPath'])) {
             return $response->withJson(['schedulerInitialized' => false]);