Error: "Setting unknown property: aki\telegram\types\Document::thumbnail" when using SendDocument

[lucadima15]

To solve the issue, I added some code locally in aki\telegram\types\Document class:

1. Added $_thumbnail property after $_thumb

2. Added magic methods:

public function getThumbnail()
{
return $this->_thumbnail;
}

public function setThumbnail($value)
{
    $this->_thumbnail = new PhotoSize($value);
}