Currently the router's internal router is only created during
``Router.map``.  If the application only has an Index then it is
reasonable that ``App.Router.map`` would never be called.

This ensures that the ``Router.map`` has been called when creating the
router.

cc @stefanpenner
fix typo
Merge pull request #2783 from ryanto/routers_router_only_created_on_map_fix

App router should always have internal router