“Undefined array key 0” when uploading an image

FileUpload::make('cover_image')
    ->label('Cover Image')
    ->image()
    ->directory('category-covers')
    ->multiple(false)
    ->maxFiles(1)
    ->nullable();

ErrorException: Undefined array key 0
 at vendor/livewire/livewire/src/Features/SupportFileUploads/WithFileUploads.php:40

// composer.json (excerpt)
"require": {
  "php": "^8.2",
        "filament/filament": "^3.3",
        "filament/spatie-laravel-translatable-plugin": "^3.3",
        "laravel/framework": "^12.0",
        "laravel/tinker": "^2.10.1",
        "spatie/laravel-translatable": "^6.11"
},

// app/Models/Category.php
namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Spatie\Translatable\HasTranslations;

class Category extends Model
{
    use HasTranslations;

    public $translatable = ['name'];
    protected $fillable = [
        'parent_id',
        'name',
        'order',
        'cover_image',
        'is_food',
    ];
}

// In CategoryResource form()
FileUpload::make('cover_image')
    ->label('Cover Image')
    ->image()
    ->directory('category-covers')
    ->multiple(false)
    ->maxFiles(1)
    ->nullable(),