unified return null usages

Author: fabpot

Firewall/ContextListener.php

@@ -171,7 +171,7 @@ private function refreshUser(TokenInterface $token)
                     $this->logger->warning(sprintf('Username "%s" could not be found.', $notFound->getUsername()));
                 }
 
-                return null;
+                return;
             }
         }
 

RememberMe/AbstractRememberMeServices.php

@@ -142,8 +142,6 @@ final public function autoLogin(Request $request)
         }
 
         $this->cancelCookie($request);
-
-        return null;
     }
 
     /**