custom-metabox error: Parameter must …. implements Countable

I see lots of errors in error_log like this:

[21-Oct-2022 17:51:42 UTC] PHP Warning: count(): Parameter must be an array or an object that implements Countable in /home/xxxx/public_html/wp-content/themes/bwhc/inc/vendors/custom-metabox/init.php on line 724

I’m not sure if your metabox plugin is the same as this one, but let me ask anyway:
Is there a fix for this?

Thank you.