Json 如何将从嵌套 Select 返回的空值转换为空数组

假设我有以下内容，

CREATE TABLE IF NOT EXISTS my_schema.user (
    id serial PRIMARY KEY,
    user_name VARCHAR (50) UNIQUE NOT NULL
);

CREATE TABLE IF NOT EXISTS my_schema.project (
    id serial PRIMARY KEY,
    project_name VARCHAR (50) UNIQUE NOT NULL,
    owner BIGINT NOT NULL REFERENCES my_schema.user (id),
    collaborators BIGINT[] DEFAULT array[]::bigint[]
);

INSERT INTO my_schema.user VALUES
 (1 ,'Mike')
,(2 ,'Peter')
,(3 ,'Roger');

INSERT INTO my_schema.project VALUES
 (1 ,'project1', 1, array[2, 3])
,(2 ,'project2', 1, array[]::integer[]);

如果我按以下方式进行查询，它工作得很好，因为至少有一个协作者:

SELECT
    s.id,
    s.project_name,
    (
        SELECT to_json(array_agg(c.*))
        FROM my_schema.user as c
        WHERE c.id = ANY(s.collaborators)
    ) as collaborators,
    json_build_object(
        'id', u.id,
        'user_name', u.user_name
    ) as user
FROM my_schema.project s
INNER JOIN my_schema.user u
    ON s.owner = u.id
WHERE s.id = 2

但如果我改变

WHERE s.id = 2

到

WHERE s.id = 1

然后在collaborators字段中返回null.

我try 了多种组合，将其转换为::BIGINT[]和使用NULLIF，但都没有效果.我做错了什么？