Warning: Invalid argument supplied for foreach() in bootstrap_barrio_preprocess_status_messages() (line 633 of bootstrap_barrio.theme)

Problem/Motivation

This warning message appears in the log:

Warning: Invalid argument supplied for foreach() in bootstrap_barrio_preprocess_status_messages() (line 633 of /var/www/html/web/themes/contrib/bootstrap_barrio/bootstrap_barrio.theme)

Steps to reproduce

In my case, display any page on the frontend.

Proposed resolution

Check if $variables['message_list'] is a non-empty countable.

Remaining tasks

Submit a patch.