On a controller i get a null error

Question

Greetings i got a small problem wen .include different tables.

viewmodel.elencoomonimi = db.ElencoOmonimis
                .Where(s => s.Nome.Contains(searchString) || searchString == null || searchString == "")
                .Include(s => s.ElencoProvinces.Select(t => t.ElencoImmobiliPerDiritti_E_Quote))
                .Include(s => s.ElencoProvinces.Select(t => t.ElencoComunis))
                .Include(s => s.ElencoProvinces.Select(t => t.ElencoImmobiliPerDiritti_E_Quote.Select(r => r.ElencoIntestatis)))

and im trying this.:

 if (elencoinsta != null)
              {
                  ViewBag.ElencoInstatiID = elencoinsta.Value;
                  viewmodel.elencointestati = viewmodel.elencoimmobiliperditti.Where(
                      e => e.Id == elencoinsta.Value).Single().ElencoIntestatis;
              }

and i get as a error: An exception of type 'System.ArgumentNullException' occurred in System.Core.dll but was not handled in user code

Additional information: Value cannot be null.

and i think its coming from .Include(s => s.ElencoProvinces.Select(t => t.ElencoImmobiliPerDiritti_E_Quote.Select(r => r.ElencoIntestatis)))