QT6 (Wayland): TMainMenu is duplicated on the designer surface.
* Lazarus 3.99 (rev main_3_99-1962-g0a7ff2fb3d)
* FPC 3.2.2 x86_64-linux-qt6
* Operating System: openSUSE Tumbleweed 20240503
* AnchorDocking and Docked Form Editor installed.
* KDE Plasma Version: 6.0.4
* KDE Frameworks Version: 6.1.0
* Qt Version: 6.7.0
* Graphics Platform: Wayland
## What happens
At design-time, a TMainMenu instance dropped onto a form is duplicated. It displays both a faux menu bar and the real one, with subsequent controls shifted downward.

This does not occur at run-time.

issue