--on-all-workspaces don't work in xfce

[odnar-dev]

Important Information

Provide following Information:

• mpv 0.34.1
• archlinux
• XFCE

Reproduction steps

run mpv with --on-all-workspaces

mpv --no-config --idle --force-window --on-all-workspaces

Expected behavior

the player is visible on all workspaces

Actual behavior

the player appears only on the last created workspace

Related

https://github.com/mpv-player/mpv/issues/4373