Redeclare the getUser method in GetResponseNullableUserEvent

This allows it to have the proper return type.
This class is actually violating variance rules. The v3 of the package
will replace it with a class not extending the other event class.

Author: stof

Event/GetResponseNullableUserEvent.php

@@ -29,4 +29,12 @@ public function __construct(UserInterface $user = null, Request $request)
         $this->user = $user;
         $this->request = $request;
     }
+
+    /**
+     * @return UserInterface|null
+     */
+    public function getUser()
+    {
+        return $this->user;
+    }
 }