diff -u b/core/modules/media/src/Plugin/Field/FieldWidget/MediaFileWidget.php b/core/modules/media/src/Plugin/Field/FieldWidget/MediaFileWidget.php
--- b/core/modules/media/src/Plugin/Field/FieldWidget/MediaFileWidget.php
+++ b/core/modules/media/src/Plugin/Field/FieldWidget/MediaFileWidget.php
@@ -144,6 +144,7 @@
    */
   public static function value($element, $input, FormStateInterface $form_state) {
     $return = parent::value($element, $input, $form_state);
+    $return['mids'] = !empty($return['mids']) ? $return['mids'] : [];
 
     $form_object = $form_state->getFormObject();
     if (!$form_object instanceOf EntityFormInterface) {