Bug in 18.6.1? Can't disable "Event Tracking"

I wanted to disable the upcoming collection of events in `Settings` > `Metrics and profiling` > `Event tracking` in my self-hosted instance of GitLab 18.6.1 by disabling the checkbox in front of `Enable event tracking` and then clicking the `Save changes` pushbutton.

However, when I do so, I get an error message that says:

The form contains the following error:

  • Kroki url is not valid. Host cannot be resolved or invalid

I suspect that there is some logic in place already that checks this (future?) URL, but it’s still missing in my install because it hasn’t been required so far.

Is that a bug?