Fix array_key_exists on objects (deprecated notice or fatal error) (#1276)

Author: luigifab

app/code/core/Mage/Catalog/Helper/Product.php

@@ -552,8 +552,8 @@ public function getDefaultProductValue($fieldName, $productType)
     {
         $fieldData = $this->getFieldset($fieldName) ? (array) $this->getFieldset($fieldName) : null;
         if (
-            count($fieldData)
-            && array_key_exists($productType, $fieldData['product_type'])
+            !empty($fieldData)
+            && ((is_array($fieldData['product_type']) && array_key_exists($productType, $fieldData['product_type'])) || (is_object($fieldData['product_type']) && property_exists($fieldData['product_type'], $productType)))
             && (bool)$fieldData['use_config']
         ) {
             return $fieldData['inventory'];