Deleting Issue Security Scheme that still has projects

You can't see issues of a project, if you delete its Issue Security Scheme (deleting issue security scheme directly in issue security scheme preview).

Issues still has deleted issue security scheme level.

My fix (it worked for me):

1. I created new issue security schem

2. I added new issue security scheme level

3. I changed id of previously create issue security scheme level
in table schemeissuesecuritylevels (we use Oracle database). I setted it to value that I guessed is missing...

4. I added user group to issue security scheme level

Probably it could be done in better way?