emberjs/data — pull request #766 by brigham (2013-02-28 14:31:19+00:00)
Title: Make belongsTo recognize id 0

Using !id to check for a null belongsTo id was causing relationships to be treated as missing.

I'm using Ember.isNone to check for null or undefined instead of ! for falsiness.

I've also added a test to check for this case.