[migration] fix bug in `CWAttributeAddOp.revertprecommit_event` The `rdefdef` attribute is set during the operation execution. In some the operation crash before this assignment. In such case `revertprecommit` raise an attribute error crashing the whole process and shadowing the original error. This changeset detect and Avoid this situation.

$(document).ready(function() {
    $('a.rhythm').click(function (event){
        $('div#pageContent').toggleClass('rhythm_bg');
        $('div#page').toggleClass('rhythm_bg');
        event.preventDefault();
    });
});