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

System.ArgumentNullException: Value cannot be null.
Parameter name: source
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at Bluedesk.DynamicWeb.Integration.ProfitPlus.StockProvider.ProfitPlusStockProvider.FindProfitStockLevel(Product product)
   at Bluedesk.DynamicWeb.Integration.ProfitPlus.StockProvider.ProfitPlusStockProvider.FindStockLevel(Product product, String unitId, StockLocation stockLocation)
   at Dynamicweb.Ecommerce.Stocks.StockLevelManager.FindStockLevel(Product product, String unitId, StockLocation stockLocation)
   at Dynamicweb.Ecommerce.Products.Product.GetUnitStock(StockLocation stockLocation, String unitId)
   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, RenderingContext renderingContext, String unitId)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProducts(ProductCollection products, Template parentTemplate, String loopName, Int32 loopCounter, Boolean renderRelatedProducts, Boolean renderRelatedLists, Boolean isRecursive, RenderingContext renderingContext)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProductsWithContext(ProductCollection products, Template parentTemplate, RenderingContext renderingContext)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProducts(ProductCollection products)
   at Dynamicweb.Ecommerce.Frontend.Frontend.ListProducts(ProductCollection products, String groupsIdent, Boolean hasBeenSorted)
   at Dynamicweb.Ecommerce.Frontend.Frontend.GetProductsFromIndexQuery(ProductCatalogShowType settingsType)
   at Dynamicweb.Ecommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.Ecommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)