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

System.NullReferenceException: Object reference not set to an instance of an object.
   at Co3.Godske.Dw.DAL.Repositories.ProductRepository.GetPrices(String[] priceLevels, User user, String command) in C:\Development\git\godske-solution\Co3.Godske.Dynamicweb\DAL\Repositories\ProductRepository.cs:line 35
   at Co3.Espresso.Dw8.PriceProviders.EspressoDefaultPriceProvider.PreparePrices(ProductCollection collection) in C:\Data\Development\git\espresso-solution\Co3.Espresso.Dynamicweb8\PriceProviders\PriceProvider.cs:line 59
   at Dynamicweb.eCommerce.Prices.PriceManager.PreparePrices(ProductCollection Products)
   at Dynamicweb.eCommerce.Frontend.Frontend.ListProducts(ProductCollection products, String groupsIdent, Boolean hasBeenSorted)
   at Dynamicweb.eCommerce.Frontend.Frontend.List(String groups)
   at Dynamicweb.eCommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.eCommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModule(DataRow& ParagraphRow)