Eloquent doesn't recognize fillable fields when adding constructor to model

I have a model Categorylike this :

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Category extends Model
{
    /**
     * @var $fillable
     */
    protected $fillable = array('title', 'slug' , 'descriptoin', 'cover', 'logo', 'parent_id');

    /**
     * @var $category_logo_pathp
     */
    protected $category_logo_path ;

    /**
     * @var $category_cover_path
     */
    protected $category_cover_path ;

    /**
     * constructor
     */
    function __construct()
    {
        $this->category_cover_path = public_path() . '/upload/image/category/cover/';
        $this->category_logo_path = public_path() . '/upload/image/category/logo/';
    }

    /**
     * relation with itself
     */
    public function parent()
    {
        return self::where('id', $this->parent_id)->first();
    }

    public function coverPath()
    {
        return $this->category_cover_path;
    }

    public function logoPath()
    {
        return $this->category_logo_path;
    }
}

When inserting a category instance with the correct data into the database, Eloquent doesn't recognize the model's fillable fields and then throws, Illuminate\Database\QueryExceptionbut when I remove the constructor from the category model, it works fine and Eloquent recognizes the fillable fields. What's causing this?