emberjs/data — pull request #518 by raycohen (2012-12-12 18:19:37+00:00)
Title: Don't trigger `findAll` when `Model.find()` is called with a `null` or `undefined` parameter

Instead throw an error. This is a much easier way to understand that you're passing a bad value to `Model.find`

so in the new behavior:
```
var postId = null;
Post.find(postId); // raises