Cannot add to collections that have not been successfully fetched

[jamesarosen]

When a ResourceCollection is created, its content is undefined (unless you pass in an Array for the content, in which case it's a non-fetchable collection), which means that attempts to pushObject will fail silently. It's fine to say that you can't add items to the collection until it's been fetched. If the fetch fails, however, content is still undefined. I think the proper solution is to add a fail callback to the fetch deferred object that creates an empty content array.