Menus: Minor bugfix in popup menus. OpenerMenuBar is not always assigned.
Menus: Minor bugfix in popup menus. OpenerMenuBar is not always assigned.

Popup menus can of course be used without a Main MenuBar, so I have
to do some extra checking first before I call InternalReset.

wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI