Form Events & Dynamic ChoiceType choices

<blockquote>Expected argument of type "App\Entity\User or null", "string" given.</blockquote>

Hello,
I have this error when i try to update the page with the location, i checked the User entity but i could'not
figure it out ! Any help would be much appreciated !

<b>Here is code for User entity:</b>

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\Collection;
use Doctrine\Common\Collections\ArrayCollection;
use Symfony\Component\Serializer\Annotation\Groups;
use Symfony\Component\Security\Core\User\UserInterface;
use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
use Symfony\Component\Validator\Constraints as Assert;


/**
 * @ORM\Entity(repositoryClass="App\Repository\UserRepository")
 * @UniqueEntity(fields={"email"}, message="I think you already registered!")
 */
class User implements UserInterface
{
    /**
     * @ORM\Id()
     * @ORM\GeneratedValue()
     * @ORM\Column(type="integer")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=180, unique=true)
     * @Groups("main")
     * @Assert\NotBlank(message="please enter an email")
     * @Assert\Email()
     */
    private $email;

    /**
     * @ORM\Column(type="json")
     */
    private $roles = [];

    /**
     * @ORM\Column(type="string", length=255, nullable=true)
     * @Groups("main")
     */
    private $firstName;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $password;

    /**
     * @ORM\Column(type="string", length=255, nullable=true)
     * @Groups("main")
     */
    private $twitterUsername;

    /**
     * @ORM\OneToMany(targetEntity="App\Entity\ApiToken", mappedBy="user", orphanRemoval=true)
     */
    private $apiTokens;

    /**
     * @ORM\OneToMany(targetEntity="App\Entity\Article", mappedBy="author")
     */
    private $articles;

    /**
     * @ORM\Column(type="datetime")
     */
    private $agreedTermAt;

    public function __construct()
    {
        $this->apiTokens = new ArrayCollection();
        $this->articles = new ArrayCollection();
    }

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getEmail(): ?string
    {
        return $this->email;
    }

    public function setEmail(?string $email): self
    {
        $this->email = $email;

        return $this;
    }

    /**
     * A visual identifier that represents this user.
     *
     * @see UserInterface
     */
    public function getUsername(): string
    {
        return (string) $this->email;
    }

    /**
     * @see UserInterface
     */
    public function getRoles(): array
    {
        $roles = $this->roles;
        // guarantee every user at least has ROLE_USER
        $roles[] = 'ROLE_USER';

        return array_unique($roles);
    }

    public function setRoles(array $roles): self
    {
        $this->roles = $roles;

        return $this;
    }

    /**
     * @see UserInterface
     */
    public function getPassword()
    {
        return $this->password;
    }

    /**
     * @see UserInterface
     */
    public function getSalt()
    {
        // not needed when using bcrypt or argon
    }

    /**
     * @see UserInterface
     */
    public function eraseCredentials()
    {
        // If you store any temporary, sensitive data on the user, clear it here
        // $this->plainPassword = null;
    }

    public function getFirstName(): ?string
    {
        return $this->firstName;
    }

    public function setFirstName(?string $firstName): self
    {
        $this->firstName = $firstName;

        return $this;
    }

    public function setPassword(string $password): self
    {
        $this->password = $password;

        return $this;
    }

    public function getTwitterUsername(): ?string
    {
        return $this->twitterUsername;
    }

    public function setTwitterUsername(?string $twitterUsername): self
    {
        $this->twitterUsername = $twitterUsername;

        return $this;
    }

    public function getAvatarUrl(int $size = null): string
    {
        $url = 'https://robohash.org/'.$this->getEmail();

        if ($size) {
            $url .= sprintf('?size=%dx%d', $size, $size);
        }

        return $url;
    }

    /**
     * @return Collection|ApiToken[]
     */
    public function getApiTokens(): Collection
    {
        return $this->apiTokens;
    }

    public function addApiToken(ApiToken $apiToken): self
    {
        if (!$this->apiTokens->contains($apiToken)) {
            $this->apiTokens[] = $apiToken;
            //$apiToken->setUser($this);
        }

        return $this;
    }

    public function removeApiToken(ApiToken $apiToken): self
    {
        if ($this->apiTokens->contains($apiToken)) {
            $this->apiTokens->removeElement($apiToken);
            // set the owning side to null (unless already changed)
            if ($apiToken->getUser() === $this) {
               // $apiToken->setUser(null);
            }
        }

        return $this;
    }

    /**
     * @return Collection|Article[]
     */
    public function getArticles(): Collection
    {
        return $this->articles;
    }

    public function addArticle(?Article $article): self
    {
        if (!$this->articles->contains($article)) {
            $this->articles[] = $article;
            $article->setAuthor($this);
        }

        return $this;
    }

    public function removeArticle(?Article $article): self
    {
        if ($this->articles->contains($article)) {
            $this->articles->removeElement($article);
            // set the owning side to null (unless already changed)
            if ($article->getAuthor() === $this) {
                $article->setAuthor(null);
            }
        }

        return $this;
    }

    public function __toString()
    {
        return $this->getFirstName();
    }

    public function getAgreedTermAt(): ?\DateTimeInterface
    {
        return $this->agreedTermAt;
    }

    public function agreedTerms(): self
    {
        $this->agreedTermAt = new \DateTime();

        return $this;
    }
}

<b>ArticleFormType</b>
class ArticleFormType extends AbstractType{

private $userRepository;

public function __construct(UserRepository $userRepository)
{
    $this->userRepository = $userRepository;
}

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        //dd($options);
        //If you don't know that syntax, it basically says that I want the $article variable to be 
        //equal to $options['data'] if it exists and is not null. But if it does not exist, 
        /** Var Article|null $article */
        $article = $options['data'] ?? null;
        $isEdit = $article && $article->getId();
        $location = $article ? $article->getLocation() : null;

        $builder
            ->add('title', TextType::class,[
                'help'=>'Choose something checky!',
            ])
            ->add('content')
            ->add('author', EntityType::class,[
                'class' => User::class,
                //'choice_label'=>'email', //to the email of users, and the same for other fields, we can even return a function
                'choice_label'=> function(User $user){
                    return sprintf('(%d) %s', $user->getId(), $user->getEmail());
                },
                'placeholder'=>'Choose a user',
                'choices'=> $this->userRepository->findAllEmailWithAlphabetical(),
                'disabled'=> $isEdit,
            ])   
           ->add('author', UserSelectTextType::class)
           ->add('location',ChoiceType::class,[
                'placeholder'=> 'Choose a location',
                'required' => false,
                'choices'=>[
                'The Solar System' => 'solar_system',
                'Near a star' => 'star',
                'Interstellar Space' => 'interstellar_space'
               ],
           ])
 
        ;

        if($location){
            $builder->add('specificLocationName',ChoiceType::class,[
                'placeholder' => 'Where exactly?',
                'choices'=> $this->getLocationNameChoices($location),
                'required'=>false,
                 
            ]);
        }

        if ($options['include_published_at']) {
            $builder->add('publishedAt', null, [ 
                'widget' => 'single_text',
            ]);
        }
        
    }
 

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'data_class' => Article::class,
            'include_published_at' =>false, //as we dont declare a such var we put it here too
        ]);
    }



    private function getLocationNameChoices(string $location)
    {
  
        //array_combine — Creates an array by using one array for keys and another for its values
        $planets = [
            'Mercury',
            'Venus',
            'Earth',
            'Mars',
            'Jupiter',
            'Saturn',
            'Uranus',
            'Neptune',
        ];
        $stars = [
            'Polaris',
            'Sirius',
            'Alpha Centauari A',
            'Alpha Centauari B',
            'Betelgeuse',
            'Rigel',
            'Other'
        ];
        $locationNameChoices = [
            'solar_system' => array_combine($planets, $planets),
            'star' => array_combine($stars, $stars),
            'interstellar_space' => null,
        ];
        return $locationNameChoices[$location];
    }
}

How can I save builder EntityType field with multiple selected options to the database (I use mysql 5.7) and when displaying edit form the "select multiple" field to have those options highlighted (with selected attribute)? I load a list of products via 'class' but on after selecting something and hit save i get error:
"<b>Unable to transform value for property path "licensed_products": Expected a Doctrine\Common\Collections\Collection object.</b>"

This is the code from my builder:
`
->add('licensed_products', EntityType::class,[

'class' => Product::class,
'choice_label' => function($choice){
    return $choice->getProductName();
},
'multiple' => true

])`

licensed_products is a string currently.