How to fix Trying to access array offset on value of type null?

Question

PHP

Greetings!
After upgrading to PHP 7.4, a bug appeared that cannot be fixed.
If the $favorites_info value does not exist, it throws an error Trying to access array offset on value of type
null

$fav_id = $goods_id;
        $favorites_model = model('favorites');
        //Вы уже добавили этот товар в избранное
        $favorites_info = $favorites_model->getOneFavorites(array(
            'fav_id' => "$fav_id",
            'fav_type' => 'goods',
            'member_id' => session('member_id')
        ));

    //$favorites_info = $favorites_info ?? ''; //я добавил этот код, но выдает ошибку Illegal string offset 'fav_id'

    View::assign('favorites_info', $favorites_info);

In the template it looks like this:
{$favorites_info.fav_id}
I added a check $favorites_info = $favorites_info ?? ''; but now it gives an error Illegal string offset 'fav_id'
Can you tell me how to fix it?
Thanks in advance for those who respond!