Post function "Copy Value From Field to Field Function" show as a conditions or validators instead when the custom field used is deleted.

Symptoms

The post function "Copy Value From Field to Field Function" shows as "Only users with Create Issues permission can execute this transition." in the create transition.
While it might be show as the conditions in the transition like "Only users with Assignable User permission can execute this transition." in another transition if the custom field used in the copy value post functions is deleted.

Error message shows that custom field cannot be found when try to create issue.
When you try to search the custom field id in jira workflow database, it can be found in the descriptor.

Steps to replicate

1. Create an customer field Client and add it to the respective project screen and field scheme.
2. Go to create transition of the workflow.
3. Add post function Copy value from field Client to Assignee.(At this stage the post function should render correctly.)
4. Delete custom field Client.
5. Go to edit the same workflow transition again, you will see that the post function show as "Only users with Create Issues permission can execute this transition." instead.

Indexing does not solve the problem.