[Security/Core] force implementations to accept null values

src/Symfony/Component/Security/Core/SecurityContextInterface.php

@@ -28,7 +28,7 @@ interface SecurityContextInterface
      * @param TokenInterface $token
      * @return void
      */
-    function setToken(TokenInterface $token);
+    function setToken(TokenInterface $token = null);
 
     /**
      * Checks if the attributes are granted against the current authentication token and optionally supplied object.