window-stack-bridge service failing

On the Xavier, there’s a system service requested, but not starting:

Oct 21 22:30:51 xavier systemd[7263]: window-stack-bridge.service: Failed to execute command: No such file or directory

This is mentioned in two places:

nvidia@xavier:~$ locate window-stack-bridge
/usr/lib/systemd/user/unity-session.target.wants/window-stack-bridge.service
/usr/lib/systemd/user/window-stack-bridge.service

/usr/lib/systemd/user/window-stack-bridge.service calls out the following ExecStart:

ExecStart=/usr/lib/aarch64-linux-gnu/hud/window-stack-bridge

However, that file doesn’t exist (as can be seen by the “locate” above, and this ls:)

nvidia@xavier:~$ ls -l /usr/lib/aarch64-linux-gnu/hud/window-stack-bridge
ls: cannot access '/usr/lib/aarch64-linux-gnu/hud/window-stack-bridge': No such file or directory

I notice that a configuration file for this service also exists in the TX2 JetPack root file system, but there’s no such service on my regular Ubuntu desktop.

What is this service, and why is it configure to start but missing its executable?