Update Serializer.php

Author: zhihuacui

src/components/Serializer.php

@@ -201,7 +201,7 @@ protected function normalizeResponse($model)
  $this->typeCastClass::cast($type, $attribute['value']);
  }
 
- if (is_numeric($i)) {
+ if (is_numeric($i) && $key) {
  $ret[$key] = $this->useModelResponse ? $attribute : $attribute['value'];
  } else {
  $ret[$i] = $this->useModelResponse ? $attribute : $attribute['value'];