laravel check if relation is null
// filter models that do not have any related items:
1. Model::has('relation')->get()
// Once you have a model, if you already have loaded the collection,
// you can check the count of the collection:
2. $model->relation->count();
// If you want to check without loading the relation,
// you can run a query on the relation:
3. $model->relation()->exists();
4. count($model->relation)
5. is_null($model->relation)