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

System.NullReferenceException: Object reference not set to an instance of an object.
   at DwCustomModules.CustomModules.ProductFilter.Frontend.GetTemplateTags(Group selectedGroup, ParagraphCollection pageParagraphCollection, Template template)
   at DwCustomModules.CustomModules.ProductFilter.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModule(DataRow& ParagraphRow)