You can’t reproduce this bug just by resizing the browser. You can reproduce it or by using chrome’s device toolbar (which emulating the mobile view). Or you can enter my site via some smartphone.
In order to use chrome’s device toolbar, you need to open the chrome, enter my site, on my site please press F12 (for windows) in order to open developer tools, then press on the mobile icon on the left upper corner. I’ve used Iphone 4 device simulation, but I think it doesn’t matter.