MVC Deleting objects with EntityFramework on Delete failure EF trashes relationships

Question

ASP.NET 4.0 MVC 2.0 EF 4.0

For my code below, the view accesses a navigation property on the img and is throwing a null reference exception when the database cannot perform the operation. This happens with both .Include on the context and LazyLoadingEnabled==true. My navigation property becomes null right after SaveChanges. But SaveChanges fails because of a foreign key restraint in the database, a pretty common scenario. It's typical to redisplay the form along with the error message, but the navigation property is permanently null. Anyone know how to fix this?

    [HttpPost]
    public ActionResult Delete(int id, FormCollection collection)
    {
        context.ContextOptions.LazyLoadingEnabled = true;
        var img = GetImageByID(id);

        try
        {
            context.DeleteObject(img);                
            context.SaveChanges();                
            return RedirectToAction("Index");
        }
        catch
        {
            ModelState.AddModelError("", "Cannot delete object");
        }            
        return View(img);        
    }