HTTP Error 500 occurs when Adding a Comment with Admin

[cocova]

It happens when I was trying to add a comment when logging in as an Admin.
I found no error output in Nginx access_log and error_log:
/var/log/nginx/error.log /var/log/nginx/access.log
But there is Error output in postgresql log: /var/log/postgresql/postgresql-12-main.log
2021-11-15 02:39:19.227 UTC [8532] mediacms@mediacms ERROR: null value in column "media_id" violates not-null constraint
2021-11-15 02:39:19.227 UTC [8532] mediacms@mediacms DETAIL: Failing row contains (12, 2021-11-15 02:39:19.226981+00, Very Good, 3049cf98-8644-4f4c-8e2f-1d31b36a46b2, 1, 2, 1, 0, null, null, null).
2021-11-15 02:39:19.227 UTC [8532] mediacms@mediacms STATEMENT: INSERT INTO "files_comment" ("add_date", "media_id", "parent_id", "text", "uid", "user_id", "lft", "rght", "tree_id", "level") VALUES ('2021-11-15T02:39:19.226981+00:00'::timestamptz, NULL, NULL, 'Very Good', '3049cf98-8644-4f4c-8e2f-1d31b36a46b2'::uuid, NULL, 1, 2, 1, 0) RETURNING "files_comment"."id"

What is the problem? And how to resolve it?

Thanks in advance.