_normalizeArguments not working properly when ({effect: "someeffect"}, callback)

Summary:

If "hide" effect for a dialog is defined, "close" event is not invoked when dialog closes.

How to reproduce:

Here is it on jsbin:

http://jsbin.com/ocesik/1/edit

$("<div></div>).dialog({
   modal: true,
   autoOpen: true,
   hide: {effect: "fade", duration: 150}, //if hide effect is defined, "close" event is not triggered
   close: function () {alert("dialog:close")}
});

Possible cause:

This results in calling of:

_normalizeArgumets({effect: "fade", duration: 150}, function () {alert("dialog:close")});

but the callback is lost after the first "if" in the _normalizeArguments function:

// here "options" parameter is "function () {alert("dialog:close")}"
if ( $.isPlainObject( effect ) ) {
   options = effect; //here the callback is lost!!!
   effect = effect.effect;
}
// here "options" is the same as "effect" parameter: "{effect: "fade", duration: 150"}, so, the callback is lost and not invoked

Possible fix:

First "if" in the function should be replaced by:

if ( $.isPlainObject( effect ) ) {
   callback = options; //the callback is not lost anymore
   options = effect;
   effect = effect.effect;
}