[5.4] Check for typos in first fluent route segment

[JosephSilber]

Currently, this will not throw:

Route::midddleware('auth')->get('/', 'HomeController@index');

But this will:

Route::as('home')->midddleware('auth')->get('/', 'HomeController@index');

---

This PR adds a guard against the first example too.

[GrahamCampbell]

Seems fair. 👍

[GrahamCampbell]

Ideally, we'd have a unit test too please. ;)