Issue #3505867: Error: Call to a member function hasLinkTemplate() on string

Closes #3505867

src/ResponsivePreview.php

@@ -6,6 +6,7 @@ use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\InvokeCommand;
 use Drupal\Core\Ajax\SettingsCommand;
 use Drupal\Core\Cache\Cache;
+use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Path\CurrentPathStack;
@@ -101,6 +102,9 @@ class ResponsivePreview {
       if (!($entity = $this->routeMatch->getParameter($entity_type_id))) {
         return NULL;
       }
+      if (!($entity instanceof EntityInterface)) {
+        return NULL;
+      }
       if ($entity instanceof NodeInterface && !$this->previewEnabled($entity->type->entity)) {
         return NULL;
       }