The custom code added CSS from the theme doesn't work and seems to be breaking the site. With the following error message: "call to menber function addStyledeclaration() on null"

I found this in the theme's documentation:

"Note! In some cases, the added custom code may not work and appears to be damaged (i-frame or s-crypt) - it is caused by RSfirewall component. Please change your settings and paste the original code again. Do not use custom php code inside of the template options!" URL: https://www.joomshaper.com/documentation/joomla-templates/podcasta/custom-css-js-and-tracking-code

However, it does not explain how to tweak RSfirewall . Can you help me adjust?

Theme used: https://www.joomshaper.com/documentation/joomla-templates/podcasta/technical-requirements

Website is in PHP8 / Joomla3