Symfony version(s) affected

7.1

Description

Hello,
When trying to upgrade to symfony 7.1 I get the following error.

!!  In DoctrineLoader.php line 129:
!!                                    
!!    Warning: Undefined array key 0 

After taking a look in the code the problem seems to be due to one of my entity validation constraints having a UniqueEntity constraint set like this :

App\Entity\User:
    constraints:
        - Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity: email

But if I define the constraint like below I don't get the warning :

App\Entity\User:
    constraints:
        - Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity:
              fields: ['email']

How to reproduce

Add a UniqueEntity constraint without using the fields option and try to validate your entity

App\Entity\User:
    constraints:
        - Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity: email

Possible Solution

No response

Additional Context

No response