[frontend] Load taxon if params[:taxon] exists in ProductsController

Fixes a small bug where searching *twice* for the same term results in the taxon 'scope' being forgotten

frontend/app/controllers/spree/products_controller.rb

@@ -1,6 +1,8 @@
 module Spree
   class ProductsController < Spree::StoreController
     before_filter :load_product, :only => :show
+    before_filter :load_taxon, :only => :index
+
     rescue_from ActiveRecord::RecordNotFound, :with => :render_404
     helper 'spree/taxons'
 
@@ -31,5 +33,9 @@ def load_product
         end
         @product = @products.friendly.find(params[:id])
       end
+
+      def load_taxon
+        @taxon = Spree::Taxon.find(params[:taxon]) if params[:taxon].present?
+      end
   end
 end