Remove usage of empty function when possible

Author: alamirault

EventListener/AbstractSessionListener.php

@@ -151,7 +151,7 @@ public function onKernelResponse(ResponseEvent $event)
                 $request = $event->getRequest();
                 $requestSessionCookieId = $request->cookies->get($sessionName);
 
-                $isSessionEmpty = ($session instanceof Session ? $session->isEmpty() : empty($session->all())) && empty($_SESSION); // checking $_SESSION to keep compatibility with native sessions
+                $isSessionEmpty = ($session instanceof Session ? $session->isEmpty() : !$session->all()) && empty($_SESSION); // checking $_SESSION to keep compatibility with native sessions
                 if ($requestSessionCookieId && $isSessionEmpty) {
                     // PHP internally sets the session cookie value to "deleted" when setcookie() is called with empty string $value argument
                     // which happens in \Symfony\Component\HttpFoundation\Session\Storage\Handler\AbstractSessionHandler::destroy