SourcedBox Design Error: 'css' is undefined

Triggered by: _base.html (line 28)

  26.         
  27.         <!-- css.base() puts in the base CSS used to style the checkout page, my account page, receipt page, etc -->
> 28.         {{ css.base() }}
  29.         {{ 'css/bootstrap.css' | asset_url | stylesheet_tag }}
  30.         {{ 'css/shop.min.css' | asset_url | stylesheet_tag }}

Stack Trace:

Traceback (most recent call last):
  File "/src/cratejoy/cratejoy/theme/render.py", line 401, in render_page
    output = tpl.render(**kwargs)
  File "/usr/local/lib/python2.7/site-packages/jinja2/environment.py", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "/usr/local/lib/python2.7/site-packages/jinja2/environment.py", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "_base.html", line 28, in top-level template code
  File "/usr/local/lib/python2.7/site-packages/jinja2/sandbox.py", line 385, in getattr
    value = getattr(obj, attribute)
UndefinedError: 'css' is undefined

PSST: If you are the owner of this store, fix this error from the code editor. See the developer documentation for more information.