[FK Menu] VOLUME/BRIGHTNESS setting display is not updated when using shortcuts while the FK menu is open

[DrUm78]

VOLUME/BRIGHTNESS setting display is not updated when using shortcuts while the FK menu is open. It's minor and not sure whether some people will do it actually, just spotting it here as the nitpicker I am. :)

Steps to reproduce the behavior:

1. Open the FK menu with MENU button while in RetroFE or GMenu2X
2. Use Fn+Y/A or Fn+X+B to modify VOLUME or BRIGHTNESS
3. Notice that the settings in FK menu do not get updated
4. Close the FK menu and open it again
5. Settings in the FK menu are now updated

Expected behavior
I think the easier way would be to deactivate those shortcuts while the FK menu is open. Indeed, it's the case for ratio shortcut (Fn+DOWN). That way that would fix the bug and there is no need to use volume/brightness shortcuts if the FK menu is open anyway.