Missing ForeignKeyContraint validation

Question

I am developing a Symfony 7.1 application. This is my User class (part of it):

<?php

namespace App\Entity;

use App\Repository\UserRepository;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Security\Core\User\PasswordAuthenticatedUserInterface;
use Symfony\Component\Security\Core\User\UserInterface;

#[ORM\Entity(repositoryClass: UserRepository::class)]
class User implements UserInterface, PasswordAuthenticatedUserInterface
{
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column]
    private ?int $id = null;

    #[ORM\Column(length: 180, unique: true)]
    #[Assert\Email(
        message: 'Die Email {{ value }} ist nicht valide.',
    )]
    private ?string $email = null;

    #[ORM\Column]
    private array $roles = [];

    /**
     * @var string The hashed password
     */
    #[ORM\Column]
    private ?string $password = null;

    #[ORM\Column(length: 255)]
    #[Assert\NotNull]
    private ?string $firstname = null;

    #[ORM\Column(length: 255)]
    #[Assert\NotNull]
    private ?string $lastname = null;

    #[ORM\ManyToOne(inversedBy: 'users')]
    #[ORM\JoinColumn(nullable: false)]
    private ?Club $club = null;

    #[ORM\ManyToOne(inversedBy: 'users')]
    private ?Squad $squad = null;

    #[ORM\Column]
    private ?bool $assistance = null;

    #[ORM\Column(type: 'boolean')]
    private $isVerified = false;

    /**
     * @var Collection<int, Group>
     */
    #[ORM\ManyToMany(targetEntity: Group::class, inversedBy: 'users')]
    private Collection $groups;

In my delete-controller I check if there is any ForeignKeyContraint:

catch (ForeignKeyConstraintViolationException $e){
$this->addFlash(
    'error',
    'Der Benutzer ' . $user->getLastname() . ' '. $user->getFirstname() .' konnte nicht  gelöscht werden. Grund: Fremdschlüsselbeziehung!'
);
}

Unfortunately, the exception is not thrown. Does anybody have an idea why? In some cases, the validation works, but here not.