CakePHP3错误解析数据库结果集

In my controller i have:

public function index()
{
    $streams = $this->Streams->find('all')->where(['user_id'=>2]);

    echo $streams->count();
    die();
    $this->set('streams', $streams);
}

When I set a user_id that has results in databse, it works fine. But when I set a user_id with not results, when I tried to loop the query or even count the results, i get the following error:

InvalidArgumentException Cannot convert value to bool

Any ideas? Thanks all!