Only return unique products from taxon_preview method

core/app/helpers/spree/taxons_helper.rb

@@ -9,6 +9,7 @@ def taxon_preview(taxon, max=4)
         taxon.descendants.each do |taxon|
           to_get = max - products.length
           products += taxon.active_products.limit(to_get)
+          products = products.uniq
           break if products.size >= max
         end
       end