Fixes failed tests for Data Object

- fixed document data provider

Author: andrewbess

lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/Document.php

@@ -10,7 +10,7 @@
 use Magento\Framework\Api\AttributeValueFactory;
 
 /**
- * Class Document
+ * The document data provider
  */
 class Document extends DataObject implements DocumentInterface
 {
@@ -33,17 +33,23 @@ public function __construct(AttributeValueFactory $attributeValueFactory)
     }
 
     /**
+     * Gets ID.
+     *
      * @return int|string
      */
     public function getId()
     {
         if (!$this->id) {
-            $this->id = $this->getData($this->getIdFieldName());
+            $this->id = $this->getIdFieldName() !== null
+                ? $this->getData($this->getIdFieldName())
+                : null;
         }
         return $this->id;
     }
 
     /**
+     * Sets ID.
+     *
      * @param int $id
      * @return void
      */