Guard the Site Settings lookup in _Layout.cshtml

[deanleigh]

Umbootstrap.Web/Views/_Layout.cshtml:5 assumes Site Settings is always present:

var siteSettings = Model.Root().FirstChild<SiteSettings>();

FirstChild<T>() returns SiteSettings?, but the value is passed straight into two partials that declare it as non-nullable:

• Views/FeaturesGlobal/header.cshtml — @inherits UmbracoViewPage<SiteSettings>
• Views/FeaturesGlobal/footer.cshtml — @inherits UmbracoViewPage<ContentModels.SiteSettings>

No warning fires today because @inherits/@model declarations are nullable-oblivious, even with <Nullable>enable</Nullable> set in the csproj. But the null is real: if the Site Settings node is missing, unpublished, or not the first child of the root, the site dies with a bare NullReferenceException somewhere inside a partial, with nothing pointing at the actual cause.

Suggested fix

Fail at the point of retrieval with a message that names the problem:

var siteSettings = Model.Root().FirstChild<SiteSettings>()
    ?? throw new InvalidOperationException(
        "The Site Settings node is missing or unpublished. It must exist as the first child of the site root.");

This also narrows the type to non-null for every downstream use, so it stays clean if anyone later introduces a strongly-typed view model taking SiteSettings.

Why this is worth doing now

In a site built from this template, adding a view model that takes a non-nullable SiteSettings immediately surfaces this as a CS8604 warning. That is exactly what happened in a downstream project (a MetaViewModel for the Head/_meta partial), and the fix belonged in _Layout rather than in the new view model.

Hardening it in the template means sites generated from it start correct, and get a useful error message instead of an NRE when an editor unpublishes the wrong node.