functions.php on line 103 error

I tried to update the theme to 2.5.3 but after doing so, I got this error. The site was working when I was running an older version with a child theme.

Any suggestions?


Hi Mark,

I hope you are well today and thank you for your question.

The wp_get_custom_css_post referred in the shared error is added in WordPress 4.7 so please make sure you are using WordPress version 4.7 or greater than it.

Best Regards,