Workrave tray icon not appearing on waybar, swaybar, or wf-shell trays

[jjramsey]

Describe the bug
Workrave tray icon not appearing on waybar, swaybar, or wf-shell trays:

• On waybar (with either labwc or hyprland), it shows a generic icon, and when waybar is started from the terminal, it displays the message, " Item 'workrave': Could not find an icon named 'workrave-icon-medium.png' and no pixmap given.".
• On swaybar (with the Sway compositor), it shows a red frowny face.
• On wf-shell (with Wayfire), the icon is completely invisible, though when the space where the icon should be is right-clicked, the Workrave menu does show up.

The nm-applet, by contrast, does not have these issues.

To Reproduce
Steps to reproduce the behavior:

1. Start Workrave.
2. Start Waybar, swaybar, or wf-shell with their tray modules enabled.

The order of 1 and 2 does not particularly matter.

Expected behavior
I should see the "sheep" icon in the system tray.

Linux (please complete the following information in case you encountered the bug on Linux):

• Distribution: Arch Linux
• Distribution Version: Rolling distro
• Workrave Version: 1.11.0-beta.14