Sortable: placeholder option class gets replaced with an object

[jbruni]

If I pass a class name as the placeholder config option when creating a sortable, I can retrieve it using sortable('option', 'placeholder') only before the placeholder is created the first time (before _createPlaceholder is called). After it, instead of returning the class name as it should, it returns an object.

See in action at ​http://jsfiddle.net/hyBfm/

It was easy to track the cause in the source code (jquery.ui.sortable.js)

At line 657, the option goes to a variable called "className". In the next line, 658, the option is overwritten by an object which serves internal purposes.

For us, end users, the behaviour of having inconsistent return values for the sortable('option', 'placeholder') is unwanted and it is not what the documentation says.

[jbruni]

Note: I had to "mutilate" the description until I could pass Akismet rejection.

[tj.vantoll]

Related to #7121.