Mnemonics appearing on startup

[Akbarkhon Variskhanov]

1) Xubuntu 20.04.3 LTS
2) xfce4-appmenu-plugin (0.7.3+dfsg1-2ubuntu0.1)
3) Mnemonics should only appear on hover or menu activation
4) Mnemonics appear on initial launch

Whenever xfce4-panel starts, xfce4-appmenu-plugin has all of the mnemonics automatically enabled, even on inactive state. To make them disappear, user has to click on any menu item, which is annoying. Another option is to add `gtk-enable-mnemonics = 0` to $HOME/.config/gtk-3.0/settings.ini, which also disables all mnemonics altogether, and that's objectively worse.

Mnemonics should not be autoshown on initial panel launch. Only on consequent hover or activation.

Screenshot included.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xfce4-appmenu-plugin 0.7.3+dfsg1-2ubuntu0.1
ProcVersionSignature: Ubuntu 5.11.0-40.44~20.04.2-generic 5.11.22
Uname: Linux 5.11.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.21
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: XFCE
Date: Sat Dec 4 17:37:55 2021
InstallationDate: Installed on 2021-05-17 (201 days ago)
InstallationMedia: Xubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
SourcePackage: vala-panel-appmenu
UpgradeStatus: No upgrade log present (probably fresh install)