Fix #10961. XRegExp's shimmed .exec() can't handle undefined.

There's no reason to call quickParse if selector is falsy, so it's a minor performance optimization anyway. No change in behavior at all on our side, so no test case needed.

src/event.js

@@ -101,7 +101,7 @@ jQuery.event = {
 				handler: handler,
 				guid: handler.guid,
 				selector: selector,
-				quick: quickParse( selector ),
+				quick: selector && quickParse( selector ),
 				namespace: namespaces.join(".")
 			}, handleObjIn );