Mysql Different order by result between inner join query and exists query

I have 2 tables in the database

1. User table has columns (name, name_ar, ...)
2. User Profile table has columns (user_id, office_id, address, mobile, ...)

the relationship between the two tables is one to one relation

Now, I'm trying to filter users by their office and order them by name_ar. I tried two different queries to do this and I expect the same result from the two queries but the result is different in order.

SELECT
    `id`, `name_ar`
FROM
    `users`
WHERE EXISTS
    (
    SELECT
        *
    FROM
        `user_profiles`
    WHERE
        `users`.`id` = `user_profiles`.`user_id` AND `office_id` = 1
) AND(
    `group` = "doctor" AND `state` = "active"
) AND `users`.`deleted_at` IS NULL
ORDER BY
    `name_ar` IS NULL, `name_ar` ASC

SELECT
    `u`.`id`,
    `name_ar`
FROM
    `users` u
INNER JOIN `user_profiles` up ON
    `u`.`id` = `up`.`user_id`
WHERE
    `group` = "doctor" AND `state` = "active" AND `up`.`office_id` = 1
ORDER BY
    `name_ar` IS NULL, `name_ar` ASC

the two results do not have the same order from the beginning of appearing null value in name_ar column (from the fifth row exactly the order is different between the two results), Can any explain for me why is this happens? Is it because of null values or another reason?

via Chebli Mohamed