Relation columns not displaying correctly

[alextepes]

Description

When adding a A17\Twill\Services\Listings\Columns\Relation column to a listing, a string of commas and spaces is displayed instead of the display field.

Steps to reproduce

use A17\Twill\Services\Listings\Columns\Relation;

    public function getIndexTableColumns(): TableColumns
    {
        $tableColumns = TableColumns::make();

        $tableColumns->add(
            Text::make()
                ->title('Title')
                ->field('title')
                ->linkToEdit()
                ->sortable(),
        );
        $tableColumns->add(
            Relation::make()
                ->relation('category')
                ->title('Category')
                ->field('title')
                ->sortable()
        );
        return $tableColumns;
    }

In the model:

    public function category()
    {
        return $this->belongsTo(Category::class);
    }

Expected result

The title of the column should be displayed on the "Category" column.

Actual result

, , , , , , , , , , , , , is displayed on the "Category" column.

Versions

Twill: 3.4.1
Laravel: 11.29
PHP 8.2.24
MariaDB