Issue #3247189 :Option A, Saving menu causes incorrect redirect.

Option A. Closes #3247189

src/BigMenuForm.php

@@ -3,7 +3,6 @@
 namespace Drupal\bigmenu;
 
 use Drupal\Core\Link;
-use Drupal\Core\Url;
 use Drupal\menu_ui\MenuForm;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Menu\MenuLinkTreeElement;
@@ -281,7 +280,7 @@ class BigMenuForm extends MenuForm {
    */
   public function save(array $form, FormStateInterface $form_state) {
     parent::save($form, $form_state);
-    $form_state->setRedirectUrl(Url::fromUserInput($this->getRedirectDestination()->get()));
+    $form_state->disableRedirect();
   }
 
   /**