Issue #3217262: Warning: array_flip(): Can only flip STRING and INTEGER values!

src/Entity/FeedType.php

@@ -214,9 +214,9 @@ class FeedType extends ConfigEntityBundleBase implements FeedTypeInterface, Enti
     // \Drupal\Core\Entity\EntityType instance which can contain a
     // stringTranslation object that is not serializable.
     // @see https://www.drupal.org/project/drupal/issues/2893029
-    $vars = array_flip($vars);
+    $vars = is_array($vars) ?: array_flip($vars);
     unset($vars['pluginCollection']);
-    $vars = array_flip($vars);
+    $vars = is_array($vars) ?: array_flip($vars);
 
     return $vars;
   }