Issue #1884148 by sun, swentel: Fixed field widget disappears when increase...

Issue #1884148 by sun, swentel: Fixed field widget disappears when increase cardinality for image to allow multiple values.

core/modules/file/lib/Drupal/file/Plugin/field/widget/FileWidget.php

@@ -141,6 +141,7 @@ protected function formMultipleElements(EntityInterface $entity, array $items, $
       // The group of elements all-together need some extra functionality after
       // building up the full list (like draggable table rows).
       $elements['#file_upload_delta'] = $delta;
+      $elements['#type'] = 'details';
       $elements['#theme'] = 'file_widget_multiple';
       $elements['#theme_wrappers'] = array('details');
       $elements['#process'] = array('file_field_widget_process_multiple');