I am having issues with using Html.RenderAction, currently I have the following in the head of the site on the master page:

@{
    Html.RenderAction("RenderMetaTags", "MetaTags");
}

This will render a partial:

@model MetaTagsModel 
@* do stuff *@

This is the controller:

public class MetaTagsController : SurfaceController
{
    public MetaTagsController()
    {

    }

    [ChildActionOnly]
    public ActionResult RenderMetaTags()
    {
        IPublishedContent currentNode = CurrentPage;
        string urlSegment = Request.Url.Scheme + "://" + Request.Url.Host;

        MetaTagsModel metaTagsModel = new MetaTagsModel()
        {
            MetaTitle = currentNode.MetaTitle(),
            MetaDescription = currentNode.MetaDescription(),
            MetaImageUrl = currentNode.MetaImage(),
            IsLiveSite = bool.Parse(ConfigurationManager.AppSettings["IsLiveSite"]),
            CanonicalUrl = urlSegment + currentNode.Url()
        };

        return base.PartialView("~/Views/Partials/Custom/Template/MetaTags.cshtml", new MetaTagsModel());
    }
}

I'm doing it this way because there'll be different logic for how meta information is pulled from the CMS and then rendered on the page. I wanted all of that logic to be in the controller and not the view (I can just use RenderPartial if it was all in the view).

I am getting the following error, which is produced by the Html.RenderAction line. Debugging never hits the controller.

[NullReferenceException: Object reference not set to an instance of an object.]
   Umbraco.Web.Mvc.ContainerControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +83
   Umbraco.Web.Mvc.UmbracoControllerFactory.CreateController(RequestContext requestContext, String controllerName) +93
   Umbraco.Web.Mvc.RenderControllerFactory.CreateController(RequestContext requestContext, String controllerName) +14
   Umbraco.Web.Mvc.MasterControllerFactory.CreateController(RequestContext requestContext, String controllerName) +53
   System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +187
   System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +50
   System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +48
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +16
   System.Web.Mvc.<>c__DisplayClass2_0.<BeginProcessRequest>b__0() +31
   System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Func`1 func) +27
   System.Web.Mvc.ServerExecuteHttpHandlerAsyncWrapper.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +98
   System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +2013
   System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +77
   System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +25
   System.Web.HttpServerUtilityWrapper.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +20
   System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) +468
   System.Web.Mvc.Html.ChildActionExtensions.RenderAction(HtmlHelper htmlHelper, String actionName, String controllerName) +35

Based on other questions/answers I've seen, and other forum posts, I can't see what I'm doing wrong?