Fullscreen for frameless windows on mac

If you have frameless window it is possible to go to fullscreen view with showFullScreen() method, but impossible to go back to normal view with showNormal() method.

I see such behavior only on Mac, on Windows everything works well.

Also it worked well on Qt 5.6.

Link to project, where I was able to reproduce the bug:

https://github.com/kosh543/fullscreentest