updated composer

vendor/symfony/http-foundation/Session/Storage/MockArraySessionStorage.php

@@ -242,7 +242,7 @@ class MockArraySessionStorage implements SessionStorageInterface
 
         foreach ($bags as $bag) {
             $key = $bag->getStorageKey();
-            $this->data[$key] = isset($this->data[$key]) ? $this->data[$key] : [];
+            $this->data[$key] = $this->data[$key] ?? [];
             $bag->initialize($this->data[$key]);
         }