Fix issue #6999: Configurable attribute cache was never hit

Author: thlassche

app/code/Magento/ConfigurableProduct/Model/Product/Type/Configurable.php

@@ -443,15 +443,15 @@ public function getConfigurableAttributes($product)
      */
     protected function hasCacheData($configurableAttributes)
     {
-        $configurableAttributes = $configurableAttributes ?: unserialize($configurableAttributes);
-        if (is_array($configurableAttributes) && count($configurableAttributes)) {
+        $configurableAttributes = $configurableAttributes ? unserialize($configurableAttributes) : $configurableAttributes;
+        if ((is_array($configurableAttributes) || $configurableAttributes instanceof \Traversable) && count($configurableAttributes)) {
             foreach ($configurableAttributes as $attribute) {
                 /** @var \Magento\ConfigurableProduct\Model\Product\Type\Configurable\Attribute $attribute */
                 if ($attribute->getData('options')) {
                     return $configurableAttributes;
                 }
             }
-        }
+      	}
         return false;
     }