view_controller_chains does not work with example #1095

Describe the bug
The output of view_controller_chains does not seem to work with the new example 12 of the demo repository.

To Reproduce
Steps to reproduce the behavior:

1. Checkout https://github.com/ros-controls/ros2_control_demos/
2. Run the example 12 as written in the doc
3. ros2 control view_controller_chains

Expected behavior
Some chain in the PDF.

Screenshots
But there are no links, just nodes:
controller_diagram.gv.pdf

Environment (please complete the following information):

• OS: Ubuntu 22.04
• Version: Rolling

Additional context
none