When deleting a pipeline, the OrgIdentitySource link is not removed

When a pipeline is deleted, the corresponding link in the OrgIdentitySource definition is not reset to NULL. If this was the one and only pipeline, the whole Pipeline input field is not displayed, so users cannot check that an old entry is still linked, not can they reset it.

To reproduce:

• define a Pipeline
• define an OIS
• link the pipeline to the OIS
• remove the pipeline

In this case, when the OIS is used during enrollment, a COPerson record is created using the deleted pipeline.

A similar problem occurs if you set the pipeline to 'Suspended'.
I expect a similar problem to exist for pipelines attached directly to Enrollment Flows.

Expected behavior:  if a pipeline is deleted, all references to the deleted pipeline should be reset. Alternatively: if a pipeline is executed, check its status first and do not run the pipeline if the status is either 'Suspended' or if the pipeline itself is soft-deleted.