AppHarborClient.GetHostnames throws ArgumentNullException

[duncansmart]

I have a simple test application enumerates sites and their hostnames:

static void apitest()
{
    var authInfo = new AuthInfo(ACCESS_TOKEN);
    var ah = new AppHarborClient(authInfo);
    foreach (var application in ah.GetApplications())
    {
        Console.WriteLine("----");
        Console.WriteLine(application.Name);
        Console.WriteLine(application.Slug);
        Console.WriteLine(application.Url);

        var hostnames = ah.GetHostnames(application.Slug);
        foreach (var hostname in hostnames)
        {
            Console.WriteLine(" * " + hostname.Id);
            Console.WriteLine(" * " + hostname.Value);
            Console.WriteLine(" * " + hostname.Url);
            Console.WriteLine(" * " + hostname.Canonical);
        }
    }
}

It blow ups at GetHostnames:

Test 'M:AppHarborTest.Program.apitest' failed: Value cannot be null.
Parameter name: url
    System.ArgumentNullException: Value cannot be null.
    Parameter name: url
    AppHarborClient.cs(184,0): at AppHarbor.AppHarborClient.CheckArgumentNull(String argumentName, Object value)
    AppHarborClient.cs(51,0): at AppHarbor.AppHarborClient.ExtractId(Uri url)
    AppHarborClient.cs(103,0): at AppHarbor.AppHarborClient.ExecuteGetListKeyed[T](RestRequest request)
    AppHarborClient.Hostname.cs(29,0): at AppHarbor.AppHarborClient.GetHostnames(String applicationSlug)
    Program.cs(50,0): at AppHarborTest.Program.apitest()

The failing code is in: AppHarborClient.ExecuteGetListKeyed:

    foreach (var item in data)
    {
        item.Id = ExtractId(item.Url);
    }

ExtractId() is throwing on a null URL.

Looking at the traffic over fiddler:

GET https://appharbor.com/applications/my-slug/hostnames

Returns:

[
  {
    "value": "my-site.example.com",
    "canonical": false,
    "url": "https://appharbor.com/applications/my-slug/hostnames/3456"
  },
  {
    "value": "my-slug.apphb.com",
    "canonical": false,
    "url": null
  }
]

Looking at the others it seems for the default apphb URLs that url us always null.