macOS menu bar with no window open is broken

[zturtleman]

The menu either doesn't show or crashes after clicking File -> New to open a window.

[zturtleman]

When a window is selected, it's menu bar is shown. When all windows are minimized, the default menu bar is shown. When a window is closed, the menu bar is empty. Restoring a minimized window shows it's menu bar. If there are no windows left, program is unusable with no menu bar. It seems like there is a Qt bug where closing window with a menu bar doesn't display the default menu.

If there is only the default menu bar (no per-window menus), it works correctly. However I haven't figure out when it's appropriate to replace the menu items. It doesn't really seem correct either.

I don't want to deal trying to build/debug Qt right now. I've reverted keeping the macOS program running with no windows open in 5d8b9b1 and moved the menu to be on the window 6bfb260.