Widget: Fix boolean option when under use strict

Fix for `options === true` when using jQuery UI under `use strict`,
which throws:
```
Uncaught TypeError: Cannot create property 'complete' on boolean 'true'
```
on line:
```js
options.complete = callback;
```

Closes gh-1931

ui/widget.js

@@ -717,6 +717,8 @@ $.each( { show: "fadeIn", hide: "fadeOut" }, function( method, defaultEffect ) {
 		options = options || {};
 		if ( typeof options === "number" ) {
 			options = { duration: options };
+		} else if ( options === true ) {
+			options = {};
 		}
 
 		hasOptions = !$.isEmptyObject( options );