Validation failure of reverse_dependencies_autopkgtest task not reported on the web

It is presently possible to create a debian_pipeline workflow that validates and runs but creates a reverse_dependencies_autopkgtest task that does not validate. Example workflow and workrequest. The debusine-server-celery has a sensible error message, but it is not mirrored into the web interface:

Error running work request Workflow/reverse_dependencies_autopkgtest (2861): orchestrator failed: 'buster' does not specify a category and the context does not supply a default