MAGETWO-56206: API - inconsistency in the Magento response data types

- Replace forced object change to instead skip empty extension_attributes (documented as optional)

Author: tjwiebell

lib/internal/Magento/Framework/Reflection/DataObjectProcessor.php

@@ -97,9 +97,9 @@ public function buildOutputDataArray($dataObject, $dataObjectType)
             if ($key === CustomAttributesDataInterface::CUSTOM_ATTRIBUTES) {
                 $value = $this->customAttributesProcessor->buildOutputDataArray($dataObject, $dataObjectType);
             } elseif ($key === "extension_attributes") {
-                $attributeArray = $this->extensionAttributesProcessor->buildOutputDataArray($value, $returnType);
-                if (!empty($attributeArray)) {
-                    $value = $attributeArray;
+                $value = $this->extensionAttributesProcessor->buildOutputDataArray($value, $returnType);
+                if (empty($value)) {
+                    continue;
                 }
             } else {
                 if (is_object($value) && !($value instanceof Phrase)) {