[5.4] fix update notification scheduled task (joomla#46315)

Author: heelc29

plugins/task/updatenotification/src/Extension/UpdateNotification.php

@@ -97,7 +97,7 @@ private function sendNotification(ExecuteTaskEvent $event): int
         $updateParams = ComponentHelper::getParams('com_joomlaupdate');
 
         // Don't send when automated updates are active and working
-        $registrationState = AutoupdateRegisterState::tryFrom($updateParams->get('autoupdate_status', ''));
+        $registrationState = AutoupdateRegisterState::tryFrom($updateParams->get('autoupdate_status', 0));
         $lastUpdateCheck   = date_create_from_format('Y-m-d H:i:s', $updateParams->get('update_last_check', ''));
 
         if ($registrationState === AutoupdateRegisterState::Subscribed && $lastUpdateCheck !== false && $lastUpdateCheck->diff(new \DateTime())->days < 4) {