allow to synchronize all articles of a shared supplier

app/helpers/articles_helper.rb

@@ -2,6 +2,7 @@ module ArticlesHelper
   
   # useful for highlighting attributes, when synchronizing articles
   def highlight_new(unequal_attributes, attribute)
+    return unless unequal_attributes
     unequal_attributes.detect {|a| a == attribute} ? "background-color: yellow" : ""
   end
 

app/helpers/suppliers_helper.rb

@@ -3,4 +3,10 @@ module SuppliersHelper
   def associated_supplier_names(shared_supplier)
     "(#{shared_supplier.suppliers.map(&:name).join(', ')})"
   end
-end
+
+  def shared_sync_method_collection(shared_supplier)
+    shared_supplier.shared_sync_methods.map do |m|
+      [t("suppliers.shared_supplier_methods.#{m}"), m]
+    end
+  end
+end