Deprecated function warning.

I get:

Deprecated function: DOMDocument::createElement(): Passing null to parameter #2 ($value) of type string is deprecated in Ups\Entity\Service->toNode() (line 160 of D:\laragon\www\drupal_contribution\vendor\gabrielbull\ups-api\src\Entity\Service.php).
Ups\Entity\Service->toNode(Object) (Line: 147)