You can of course use standard keyboard shortcuts or the Windows task bar as other ways to close any window ...
They just sent 44 - without Reborn - to the Beta stream, so you can expect the next Developer build with Reborn (probably next Tuesday) to be called Opera 45. But I don't have a crystal ball to see what bugs will be fixed by then. If it's been mentioned here or in the corresponding blog post - that's all I can suggest between now and then.