mongoid/mongoid — pull request #1874 by noniq (2012-03-30 10:12:23+00:00)
Title: Fix bug in nested attributes with reject_if all_blank and _destroy.

REJECT_ALL_BLANK_PROC does not work correctly when _destroy has a non-blank,
non-truthy value (like "0" or "false"). This can happen when using a hidden
form field instead of a checkbox, for example.

See https://github.com/rails/rails/blob/master/activerecord/lib/active_record/nested_attributes.rb#L223