How to fix error with multiple upload with Symfony 4 NoSuchPropertyException - php

Question

I want to add a field for upload many attached files in a form with Symfony 4. I've two Entity, Member and Documents with a One-To-Many relation but I've an error who doesn't mean anything for me.
In my Entity Document I've this :
/**
* #ORM\ManyToOne(targetEntity="App\Entity\Member", inversedBy="document")
*/
private $member;
/**
* #return mixed
*/
public function getFile()
{
return $this->file;
}
/**
* #param mixed $file
*/
public function setFile($file): void
{
$this->file = $file;
}
public function getMember(): ?Member
{
return $this->member;
}
public function setMember(?Member $member): self
{
$this->member = $member;
return $this;
}
In my Member Entity :
/**
* #ORM\Entity(repositoryClass="App\Repository\MemberRepository")
*/
class Member
{
/**
* #ORM\OneToMany(targetEntity="App\Entity\Documents", mappedBy="member", cascade={"persist"}, orphanRemoval=true)
*/
private $document;
public function __construct()
{
$this->years = new ArrayCollection();
$this->document = new ArrayCollection();
$this->atelier = new ArrayCollection();
}
/**
* #return Collection|Documents[]
*/
public function getDocument(): Collection
{
return $this->document;
}
public function addDocument(Documents $document): self
{
if (!$this->document->contains($document)) {
$this->document[] = $document;
$document->setMember($this);
}
return $this;
}
public function removeDocument(Documents $document): self
{
if ($this->document->contains($document)) {
$this->document->removeElement($document);
// set the owning side to null (unless already changed)
if ($document->getMember() === $this) {
$document->setMember(null);
}
}
return $this;
}
}
I've try to dump the value of my form but when I try to send my form, I've this error when I don't understand
Could not determine access type for property "document" in class "App\Entity\Member": The property "document" in class "App\Entity\Member" can be defined with the methods "addDocument()", "removeDocument()" but the new value must be an array or an instance of \Traversable, "App\Entity\Documents" given.