Hello,
Read this comment and our answer to be able to update theme via Dashboard https://themeforest.net/item/xstore-responsive-woocommerce-theme/15780546/comments?page=187&filter=all#comment_26000766
The mentioned error comes to some third-party file, it’s not our theme file, so contact WordPress support about this.
To update theme using autoupdates follow the steps described in the comment or use FTP method to update theme https://xstore.helpscoutdocs.com/article/63-theme-update
Regards
