The meaning of this field changed, it's "reversed" now, only contains fields to set to `NULL` when falling back.

So, if nothing is found with current filters, it'll first try to set region to `NULL` ;
If this doesn't work, it'll reset region to its original value and try to set carrier to `NULL` ;
If this doesn't work, the last attempt will try to set both region and carrier to `NULL`. 
If present, category is kept untouched at all times.