Fix warning
Fix warning

Fixed this warning while using the plugin:
```
Warning Error: Argument 2 passed to Ceeram\Blame\Event\LoggedInUserListener::beforeSave() must be an instance of Cake\ORM\Entity, instance of App\Model\Entity\Post given, called in /var/www/blog/vendor/cakephp/cakephp/src/Event/EventManager.php on line 389 and defined in [/var/www/blog/vendor/ceeram/cakephp-blame/src/Event/LoggedInUserListener.php, line 52]
```
ceeram/blame