Provide correct `ViewDataDictionary<TModel>.ModelMetadata` when `Model` is `null`

[dougbu]

create views (any view where Model==null) currently have ViewData.ModelMetadata.ModelType==typeof(object) and calculated ModelMetadata for properties have metadata.ModelType==typeof(string). the problem prevents correct operation of @Html.Editor() and similar helpers. for example @Html.EditorFor(model => model.Alive) in a create view returns <input type="text" .../> though Alive is a bool property and should have <input type="checkbox" .../>.

fix here is very small. should be done in the ViewDataDictionary<TModel>.ModelMetadata getter.

[dougbu]

hmm, removing last (incorrect) sentence in description.

[dougbu]

Problem reproduces consistently if the project contains a _ViewStart.cshtml file, even one that's empty.