emberjs/ember.js — pull request #3312 by bcardarella (2013-09-03 00:58:01+00:00)
Title: Notify of _subController property change

When ArrayControllers instantiate an itemController and insert into the
_subControllers array the member it replaces is `undefined`. This fix
will push a notification for property change when the actual
itemController replaces the `undefined` item.