yiisoft/yii — pull request #806 by joni (2012-06-09 20:12:32+00:00)
Title: Setting `timestampAttribute` to null when CDateValidator allows empty values

By the documentation, `timestampAttribute` should get set when the date is valid. If the validator is set to allow empty values, it's logical that timestampAttribute should be set to empty (i.e. null) when the original attribute is set to null / empty.