laravel/laravel — pull request #1363 by franzliedke (2012-10-17 15:31:33+00:00)
Title: Many-to-many sync: always work with arrays

When fetching an array of values from input, the value might be `null` if nothing was selected (instead of an empty array).

As this feels like a somewhat common use-case, this type-casting should be handled in the `sync()` method, I'd say.

http://forums.laravel.com/viewtopic.php?id=3057