I have made a object states group named "preprod_prod" with two object states "preprod" and "prod"

I have modified anonymous role to read only content with object states "prod"

If i delete the preprod_prod group and i return to the anonymous role administration, i have this error :

Fatal error: Call to a member function attribute() on a non-object in D:\Projets\CMS\xampp\htdocs\ez41\kernel\private\classes\ezcontentobjectstategroup.php on line 710
Fatal error: eZ Publish did not finish its request

The execution of eZ Publish was abruptly ended, the debug output is present below.

To rectify this, i have to recreate the object states group (with exact identifier) and modifiy my role.

Steps to reproduce

create an object states group
create 2 object states
modify anonymous role to read only content with a specific object states
delete object states group
modify anonymous role