Hi!
I have an idea how to avoid empty links in Navigation field.
Also, this method will very useful for SEO, because circle (looped) links creating more page weight (Google PR).
So, we should add 2 parameters:
1. Looped links inside current category.
When we previous link is last in current category - next item is first from current category:
and viсe versa
2. Looped links in configured parent category.
In this mode we should set parent category with subcategories in which links will be looped.
For example, parent category: Auto, subcategories: BMW, AUDI, OPEL
So, in last item in BMW category, next item is first in AUDI category:
So, we have 2 looped modes, inside current category and inside configured category including subcategories.