Which piece of code?
Edit your 'theme.liquid" file by looking for
{%- if page_description -%}
that entire section of code should go from
{%- if page_description -%}
{%- endif -%}
to
{%- if page_description -%}
{% if template == 'list-collections' %}
{% else %}
{%- endif -%}
{%- endif -%}
The line where I have “settings.metadescriptioncollections” is because I set a field in the theme settings so it can be managed from there, rather than hard coding it into the theme.liquid file.