MVC :: NullReferenceException: Object Reference Not Set To An Instance Of An Object

I am trying to post some information back to the database in this Controller Action. This Action is called when Save button is clicked on the View.

[AcceptVerbs(HttpVerbs.Post)] public ActionResult EditDetail(int id, FormCollection fvals){ Environments env = environmentsRepository.GetEnvironmentDetail(id); UpdateModel(env); environmentsRepository.Save();return RedirectToAction("List", new RouteValueDictionary(new {controller="Environments", action="List", id = 1})); }

When I click on the Save button, I get the following error:

Line 32:
Line 33:
Line 34: <% foreach (var environment in Model) <--Error in this line
Line 35: { %>
Line 36:

[NullReferenceException: Object reference not set to an instance of an object.] ASP.views_environments_list_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in e:codeosspWebUIViewsEnvironmentsList.aspx:34