Empty files wipe out configuration

[utricularian]

If I have an empty yaml file in an environment, but a fleshed-out yaml file in common, then configoro loads with that key as nil

In common/foo.yml

---
  bar: baz

In development/foo.yml

---

If I load up in development, then MyApp::Configuration.foo == nil

I expect MyApp::Configuration.foo.bar == 'baz'