note: I'm using a theme I bought from uskinned.

when I navigate to a page ("pageA")(id: 1183) with document type DocTypeA that has the following template:

@inherits Umbraco.Web.Mvc.UmbracoTemplatePage @{ Layout = "master.cshtml"; } . .

.

and master.cshtml is @inherits Umbraco.Web.Mvc.UmbracoTemplatePage @{ Layout = null; } . . @Html.Partial("section/SEOPageHead", @Model.Content) <-- Line B .

.

and SEOPageHead.cshtml is @inherits Umbraco.Web.Mvc.UmbracoTemplatePage @{ IPublishedContent homeNode = Model.Content.AncestorOrSelf(1); <-- Line C .

.

there are no errors.

If I hover over Model in line B or C above in debug mode, I see both Model.Content and Model.CurrentCulture.

I then followed http://shazwazza.com/post/Custom-MVC-routing-in-Umbraco to implement the following custom route localhost/cars/views/3

using the class..

public class CarChartsController : Umbraco.Web.Mvc.PluginController
{

    public CarChartsController ()
        : this(UmbracoContext.Current)
    {
    }

    public CarChartsController (UmbracoContext umbracoContext)
        : base(umbracoContext)
    {
    }

    public ActionResult Views(string id)
    {

        var y = umbracoContext.ContentCache.GetById(1183); //this is the same doc id as pageA/DocTypeA from the very top
        return View("~/Views/views.cshtml", CreateRenderModel(y));
    }

    private RenderModel CreateRenderModel(IPublishedContent content)
    {
        var model = new RenderModel(content, CultureInfo.CurrentUICulture);

        //add an umbraco data token so the umbraco view engine executes
        RouteData.DataTokens["umbraco"] = model;
        //new UmbracoHelper()
        return model;
    }

}

views.cshtml is

@inherits Umbraco.Web.Mvc.UmbracoTemplatePage @{ Layout = "USNMaster.cshtml";

} . . .

now if navigate to localhost/cars/views/3, I get a system.nullreferenceexception error during debug.

now if I change Line B to @Html.Partial("section/SEOPageHead", @Model) // @Model.Content replaced by @Model

everything works when I navigate to the custom route localhost/cars/views/3.

Any ideas why the partial view when going via custrom route didn't work originally but did work when going through the normal umbraco route?