Workaround for Laravel 12.10.1 relation loading regression in getAttribute()

[tabuna]

This patch introduces a compatibility fix for a behavior change in Laravel introduced in laravel/framework#55471, where getAttribute('relation.key') would previously return null if the relation was a plain array, but now throws an exception.

Example:

$model->setRelations([
    'many' => [
        'one',
        'two',
        'three' => 84,
    ]
]);

$value = $model->getAttribute('many.three');
// Previously returned null, now throws