An error occurred while attaching module (Dynamicweb.Frontend.Content)

System.NullReferenceException: Object reference not set to an instance of an object.
   at Dynamicweb.Ecommerce.Frontend.Renderer.FixPathAndQuery(String pathAndQuery, String groupId)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProduct(Product product, Boolean extendedProperties, Template template, Int32 loopCounter, Boolean renderRelated, String productUrl, Int32 quantity, Int32 wishListId, Boolean renderPublicList, Boolean isRecursiveCall, Lazy`1 categoryFieldSorting, Int32 orderLineOfProductCount)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProducts(ProductCollection products, Template parentTemplate, String loopName, Int32 loopCounter, Boolean renderRelatedProducts, Boolean renderRelatedLists, Boolean isRecursive)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProducts(ProductCollection products, Template parentTemplate, String loopName)
   at Smartpage.Product.Related.ProductExtender.ExtendTemplate(Template template) in C:\Novicell Solutions\SGMLight.Website\Smartpage.Product.Related\ProductExtender.cs:line 21
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProductTemplateExtenders(Product product, Template template, Boolean extendedProperties)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProduct(Product product, Boolean extendedProperties, Template template, Int32 loopCounter, Boolean renderRelated, String productUrl, Int32 quantity, Int32 wishListId, Boolean renderPublicList, Boolean isRecursiveCall, Lazy`1 categoryFieldSorting, Int32 orderLineOfProductCount)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProduct(Product product, Boolean extendedProperties)
   at Dynamicweb.Ecommerce.Frontend.Frontend.RenderProduct(Product product)
   at Dynamicweb.Ecommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.Ecommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)