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

System.NullReferenceException: Object reference not set to an instance of an object.
   at DanskRideForbund.CustomModules.RiderModule.RiderModuleFrontend.ShowRider(RiderHelper helper, DataArea dataArea) in D:\a\1\s\Application\CustomModules\RiderModule\RiderModuleFrontend.cs:line 154
   at DanskRideForbund.CustomModules.RiderModule.RiderModuleFrontend.GetContent() in D:\a\1\s\Application\CustomModules\RiderModule\RiderModuleFrontend.cs:line 49
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)