Warning after enable the module

After enable the module, when visit the contact form edit page i get this error

Warning: array_flip(): Can only flip STRING and INTEGER values! in Drupal\Core\Entity\EntityStorageBase->loadMultiple() (line 227 of core/lib/Drupal/Core/Entity/EntityStorageBase.php).

This is because on line 68 node is loaded without check if node_id is a valid id.

 66   // default entity_autocomplete get a node object as default value
 67   $node_id = $contact_form->getThirdPartySetting('contact_ajax', 'load_from_uri', FALSE);
 68   $node = Node::load($node_id);