Macro Rendering Error

File: app/rcloneui.md

UndefinedError: 'None' has no attribute 'startswith'

Traceback (most recent call last):
  File "/opt/buildhome/.local/share/mise/installs/python/3.13.12/lib/python3.13/site-packages/mkdocs_macros/plugin.py", line 703, in render
    return md_template.render(**page_variables)
           ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
  File "/opt/buildhome/.local/share/mise/installs/python/3.13.12/lib/python3.13/site-packages/jinja2/environment.py", line 1295, in render
    self.environment.handle_exception()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/buildhome/.local/share/mise/installs/python/3.13.12/lib/python3.13/site-packages/jinja2/environment.py", line 942, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "<template>", line 7, in top-level template code
  File "_includes/app.md", line 3, in top-level template code
    {% if _store_slug.startswith("product-category/") %}
    ^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/buildhome/.local/share/mise/installs/python/3.13.12/lib/python3.13/site-packages/jinja2/utils.py", line 92, in from_obj
    if hasattr(obj, "jinja_pass_arg"):
       ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
jinja2.exceptions.UndefinedError: 'None' has no attribute 'startswith'