.attr() returns attribute value instead of current node set if the second argument is undefined.

Code to reproduce: http://jsfiddle.net/oraz/zDNCb/

In the following examples .attr() returns current node set:

1. when we pass object like {someAttr: undefined} as only argument: http://jsfiddle.net/oraz/aBnb4/

2. when we pass null as the second argument: http://jsfiddle.net/oraz/3frQB/

Environment:

• jQuery 1.6.4
• jQuery 1.6.2
• Firefox 7
• Google Chrome 14
• IE 8

Possible fix at line 1956:

attr: function( name, value ) {
   if(arguments.length == 2 && value === undefined) {
        value = null;
   }
   return jQuery.access( this, name, value, true, jQuery.attr );
}