todo / routing / first code block isn't showing the right bits

[Greg Manning]

Code is trying to show filter getting into view_main, but shows view_footer instead:

fn view(model: &Model) -> Vec<Node<Msg>> {
    ...
            view_footer(&model.todos, model.filter),
...

fn view_main(todos: &BTreeMap<Ulid, Todo>, selected_todo: Option<&SelectedTodo>, filter: Filter) -> Node<Msg> {
    ...
        view_todo_list(todos, selected_todo, filter),
...

(I'll probably fix up these issues when I get to the end of the tutorial)