Fix media library form in workspaces.

Closes #3147148

core/modules/media_library/src/Form/AddFormBase.php

@@ -14,6 +14,7 @@
 use Drupal\Core\Form\BaseFormIdInterface;
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Form\WorkspaceSafeFormInterface;
 use Drupal\Core\Render\Element;
 use Drupal\Core\Security\TrustedCallbackInterface;
 use Drupal\Core\Url;
@@ -27,7 +28,7 @@
 /**
  * Provides a base class for creating media items from within the media library.
  */
-abstract class AddFormBase extends FormBase implements BaseFormIdInterface, TrustedCallbackInterface {
+abstract class AddFormBase extends FormBase implements BaseFormIdInterface, TrustedCallbackInterface, WorkspaceSafeFormInterface {
 
   /**
    * The entity type manager.