categories by size (descending) not working

[paul-hammant]

trafficstars

I'm doing something wrong, obviously, but the following doesn't work:

jekyll_sort: src: categories_list direction: down by: size dest: categories_list_by_size

Specifically, when categories_list_by_size is used in a for-loop, that loop is empty. 'size' is the property that says now many there are in that category.