Log Message:
Update ruby-activemodel32 to 3.9.2.

## Rails 3.2.9 (unreleased)

*   Due to a change in builder, nil values and empty strings now generates
    closed tags, so instead of this:

        <pseudonyms nil=\"true\"></pseudonyms>

    It generates this:

        <pseudonyms nil=\"true\"/>

    *Carlos Antonio da Silva*