Can't store user_id into another table in flutter - flutter

Question

I need to create a table that will add the user_id as another data in the table. But somehow my solution does not work.
The table user looks like this:
CREATE TABLE user(
user_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
username TEXT NOT NULL,
password TEXT NOT NULL,
f_name TEXT NOT NULL,
l_name TEXT NOT NULL,
email TEXT NOT NULL,
phone INTEGER NOT NULL
)
After the login, the user have to fill in a form, the data goes to the table, flowerbook:
CREATE TABLE flowerbook(
book_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
deliver_date TEXT NOT NULL,
arrangement TEXT NOT NULL,
flower_type TEXT NOT NULL,
user_id INTEGER NOT NULL
)
I tried doing this, on the submit button of the form:
onPressed: () {
Flowerbook flowerbook = Flowerbook(
deliver_date: dateController.text,
flower_type: checkboxController.text,
arrangement: dropdownController.text,
user_id: widget.user.user_id,
);
Flowerbook.register(flowerbook);
},
But I still get this error:
[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: DatabaseException(NOT NULL constraint failed: flowerbook.user_id (code 1299 SQLITE_CONSTRAINT_NOTNULL)) sql 'INSERT OR REPLACE INTO flowerbook (book_id, deliver_date, arrangement, flower_type, user_id) VALUES (NULL, ?, ?, ?, NULL)' args [1/1/2023 12:00:00, Box, Carnation]
As you can see, the delivery_date, flower_type, and arrangement is successfully added as an argument. But user_id is NULL.
What seems to be the problem here?
I did log the widget.user.user_id, and it is indeed NULL.
Maybe there's something wrong at my menu page? Here's my code:
final List<Widget> _widgetOptions = <Widget>[
FormPage(user: widget.user),
OrderPage(user: widget.user),
AccountPage(user: widget.user),
];