mongoid/mongoid — pull request #2399 by tiagogodinho (2012-09-24 15:04:28+00:00)
Title: Fixes a bug when passes blank values to _ids accessor

**SimpleForm** appends a hidden field to make sure something will be sent back to the server if all checkboxes are unchecked.

``` html

1808

```

Mongoid receives `"category" => {"product_ids"=>[""]}` and return **DocumentNotFound**.