Block Helper and Em.Select context

[fsmanuel]

I'm not sure if this is a handlebars bug or a ember bug or nothing of that and i just get it wrong.

I'm using the each helper and inside of it i have a Em.Select with a contentBinding on "controllers.exchanges.optionsForSelect" (using needs: ['exchanges'] in the controller).
Outside of the each helper that works. Inside i changed the binding to "../controllers.exchanges.optionsForSelect" to access the parent context. Now i get an error:
Uncaught TypeError: Cannot read property '0' of null in

function firstKey(path) {
  return path.match(FIRST_KEY)[0];
}

Why isn't that working? How can I bind a Em.Select to the parent context?
I appreciate any suggestions (helpers, etc). I have no idea how i should solve this.
I read #196 but it seems that it doesn't apply to ember bindings.

JsFiddle: http://jsfiddle.net/vZRh2/

[wagenet]

@fsmanuel Using the controller keyword works: http://jsfiddle.net/vZRh2/1/. If you're still having issues, you should probably refile on Ember.