Fix overwriting an array element

Author: wkania

Extension/Core/Type/WeekType.php

@@ -42,7 +42,6 @@ public function buildForm(FormBuilderInterface $builder, array $options)
         } else {
             $yearOptions = $weekOptions = [
                 'error_bubbling' => true,
-                'empty_data' => '',
             ];
             // when the form is compound the entries of the array are ignored in favor of children data
             // so we need to handle the cascade setting here