Default workflow remains configured after workflow deletion

[lcjohnso]

Current behavior

When a workflow is designated as a project's default workflow and then deleted, the configuration.default_workflow field on the project resource remains set with the now-deleted workflow's ID. This state leads to an error when trying to load the classifier: the console replies that there are no active workflows after trying and failing to load the now-deleted default workflow.

Expected behavior

Maybe: upon workflow deletion, the default_workflow configuration variable is cleared. Or: if default workflow is not found, workflow selection moves on to a random choice drawn from active workflows.

Steps to replicate

1. Create workflow and enable default workflow option in workflow editor.
2. Delete the now-default workflow.
3. From project landing page when project has at least one active workflow, choose "classify" or "get started".

Additional information

Based on Talk thread (link here) report by Sea Lion Aotearoa project (ID = 17937).