Deleted user in Crowd creates trouble in Jira when the user have tasks assigned

We use Crowd for external user management.
Yesterday I removed a user in Crowd that resigned his position.
At least one issue in Jira was assigned to this user.

When we try to edit the issue assigned to the no-longer-existing-user, Jira throws server error (see attached file).

I believe Jira should disable the user but not delete it?