Object reference not set to an instance of an object.

at System.Collections.Specialized.NameObjectCollectionBase.BaseRemove(String name) at System.Web.SessionState.SessionStateItemCollection.Remove(String name) at UniversalWEBPlatform.MODDati.VerifyComponentAsyncTeminate(ResultBlock& result, HttpSessionState& Session, List`1& ElencoIMG, List`1& ElencoIMGPrefer, DataClass BaseClass, String PageName) at UniversalWEBPlatform.MODLayout.CostruisciPagina(Pagina& Pagina, String RouteString, HttpServerUtility& Server, HttpResponse& Response, HttpRequest& Request, HttpSessionState Session, DataClass BaseClass, ParameterRetHtmlString& Parameter, List`1& ElencoIMG, List`1& ElencoIMGFetchPrefer, String& CanonicalLink, String& MasterTitleString, String& MasterDescriptionString, Boolean& HasCheckOUT, String& MasterMetaOGString, Boolean Preview) at UniversalWEBPlatform.Pagina.Page_Load(Object sender, EventArgs e)