addClass seems to trigger Invalid argument in IE in jquery 1.5.1

[bluefox]

Can be reproduced by going to  http://jqueryui.com/demos/addClass/ with IE (8.0.7600.16385) and click Run Effect. A script error is generated

Invalid argument. jquery.min.js, line 16 character 79183

Might be a conflict with jQuery 1.5.1?

[scott.gonzalez]

This is caused by a change in 1.5.1:  https://github.com/jquery/jquery/commit/85d9343271da85fc945bf37a604873eaf247a3a7

[scott.gonzalez]

jQuery core bug:  http://bugs.jquery.com/ticket/8627

[gnarf]

In the meantime, while waiting for jQuery Core to catch up to this bug, you can use this cssHook to fix this error:

$.cssHooks.letterSpacing = {
    get: function ( elem, computed ) {
        var ret = parseFloat( elem.style.letterSpacing ) || 0;
        return ret;
    }
};

 http://jsfiddle.net/gnarf/bkd4S/3/

[scott.gonzalez]

gnarf: Any reason not to just land that cssHook in UI core? If $.cssHooks exists, define it, if not, don't do anything. That should handle all versions, right? We can land that in master and merge into 1-8-stable.

[scott.gonzalez]

This is fixed in jQuery core.