Sending data with trigger differs between version 1.5 and 1.6.1. I can't figure out what causes this behaviour from reading the official change log.

With 1.6.1 => undefined, undefined

With 1.5.0 => (an empty string), undefined

$(document).ready(function() {
$("p").click( function (event, a, b) {
console.log(a);
console.log(b);
} ).trigger("click", '');
});