notification: add test for unread consistency

src/Bundle/ChillMainBundle/Form/NotificationType.php

@@ -28,6 +28,7 @@ class NotificationType extends AbstractType
                 'class' => User::class,
                 'choice_label' => 'label',
                 'multiple' => true,
+                'by_reference' => true,
             ])
             ->add('message', ChillTextareaType::class, [
                 'required' => false,