Problem with sortable options in jquery ui 1.8.1

Problem with sortable options in jquery ui 1.8.1

First of all, good day to everyone, and sorry for my poor english... i hope that you can understand my problem.

Today i was dealing with a problem in a function that was using ui 1.7.2 and i changed the version of the ui to 1.8.1.
The function started to throw an error while it was trying to asign the event "stop" to the selector. The code is similar to this

$(function() {
    $("#" + contenedor).sortable({
        stop: function(event, ui) {
            ...
            code
            ...
        },
        ...
        code
        ...
    });
...

when i started to look into the ui I saw that the problem it was generated in this piece of code of ui.sortable :

_setOption: function(key, value){
if ( key === "disabled" ) {
this.options[ key ] = value;
this.widget()
[ value ? "addClass" : "removeClass"]( "ui-sortable-disabled" );
} else {
// Don't call widget base _setOption for disable as it adds ui-state-disabled class
$.Widget.prototype._setOption.apply( self, arguments);
}
},

the parameter "self" of the _setOption correspond to the javascript self, and in this case, to the entire document instead of the selector.

now the code looks like this:

_setOption: function(key, value){
if ( key === "disabled" ) {
this.options[ key ] = value;
this.widget()
[ value ? "addClass" : "removeClass"]( "ui-sortable-disabled" );
} else {
// Don't call widget base _setOption for disable as it adds ui-state-disabled class
$.Widget.prototype._setOption.apply( this, arguments);
}
},

and the problem was gone.

the question is: ¿This is really a problem of the ui or I am doing something wrong?
if you have the same problem or have an idea of whats going on, please, post a comment because this is giving me a really big headache...

thank you in advance