Pipeline visualization disappears when adding broken dependencys

[benpowis]

As a user I am able to add conflicting dependencies to a job, which then makes the pipeline page a blank screen. I can navigate to the jobs screen and see the job with multiple dependencies, but when I click to edit it I also get an empty screen. If I delete the job, then this fixes the issue and the pipeline appears again, although without the job that I broke!

It would be better if there was an error/blocker to stop a user applying broken dependencies initially.