The search widget is causing an error on submit

Hello,

there is a problem with the search script […]/start-blogging/template-parts/content-search.php.

Submitting the search box included as a widget in the right sidebar the following error message appears:
Fatal error: Call to undefined function start_blogging_custom_excerpts() in […]/themes/start-blogging/template-parts/content-search.php on line 32

I think the problem is in line 61 where the script is calling the function mentioned in the error message.

Please note that I fixed it temporary on my website – no error occurs there at the moment.
I have replaced the necessary lines out and replaced it with the WordPress function the_excerpt();.
But I think this should be just a temporary solution. With the next update of your theme I have to fix it again.

Would you be so kind to check this issue?

Thanks in advance.

Best regards,
Claudia

Theme: Start Blogging

The page I need help with: [log in to see the link]