Enqueue Wordpress media library assets on form editor page

[MAILPOET-2750]

lib/AdminPages/Pages/FormEditor.php

@@ -96,6 +96,7 @@ class FormEditor {
       'sub_menu' => 'mailpoet-forms',
       'custom_fields' => $this->customFieldsResponseBuilder->buildBatch($customFields),
     ];
+    $this->wp->wpEnqueueMedia();
 
     $this->pageRenderer->displayPage('form/editor.html', $data);
   }