Application notificaions don't dissapear under Wayland

Issue Description

I'm running Xfce 4.20 with labwc on Arch Linux started by lightdm. I have volume control commands through rc.xml that execte pactl. They generate notifications that disappear. However the application notifications (e.g. Chromium, Thunderbird) stay until they are clicked on. The notifyd settings are configured for disappearing in 10 seconds.

Steps to Reproduce Issue

1. Start Xfce Wayland via lightdm
2. Start Thunderbird
3. Get new email
4. The notification doesn't disappear

Versions

• OS distribution and version: Arch Linux up to date
• Overall Xfce version: 4.20
• xfce4-notifyd version (git hash if not a release): 0.9.6
• Windowing system (X11/Wayland): Wayland
• Compositor and version (if Wayland): labwc 0.8.2