eloquent-json-relations: eager load use with method，show error “array_key_exists() expects parameter 2 to be array, null given”

My Code as follows：

class CourseCategory extends Model
{
    use \Staudenmeir\EloquentJsonRelations\HasJsonRelationships;

    public function teachers()
    {
        return $this->hasManyJson(Teacher::class, 'courses[]->category');
    }

}

class Teacher extends Model
{
    use \Staudenmeir\EloquentJsonRelations\HasJsonRelationships;

    protected $casts = [ 
        'courses' => 'json',  
    ];
 
    public function courseCategories()
    {
        return $this->belongsToJson(CourseCategory::class, 'courses[]->category');
    }

}

the json column data sample:

[{"main_category":21,"category":33,"course":[85]},{"main_category":20,"category":25,"course":[88]},{"main_category":37,"category":40}]

When I use CourseCategory::find(33)->teachers , is ok， but I use CourseCategory::with('teachers')->find(33) , show error array_key_exists() expects parameter 2 to be array, null given

I check vendor/staudenmeir/eloquent-json-relations/src/Relations/HasManyJson.php:221

    protected function pivotAttributes(Model $model, Model $parent)
    {
        $key = str_replace('->', '.', $this->key);
     
        $record = collect($model->{$this->getPathName()})
            ->filter(function ($value) use ($key, $parent) {
                return Arr::get($value, $key) == $parent->{$this->localKey};
            })->first();
        
        return Arr::except($record, $key);
    }

I found $parent->{$this->localKey} is null