Problem applying conditions against results back from a database

[card51shor]

OK well I am entering the data. I have a registration code here :

@app.route("/register", methods=["GET", "POST"])
def register():
    
    if request.method == "GET":
        return render_template("register.html")
    elif request.method == "POST":
        password = request.form.get("password")
        username = request.form.get("username")
        session.clear()
        db.execute("INSERT INTO users (username, password) VALUES (:username, :password)", {"username":username, "password":password})
        db.commit()
        return render_template("login.html")

the issue with my app is:

1) When I login with the incorrect username and password - i get an error.
2) When I login with a correct username and incorrect password - it works.
3) When I login with correct username and correct password - it works.

It only doesn't work on the first option when both are wrong - it gives me an error like this :

Error:
TypeError

TypeError: 'NoneType' object is not subscriptable
Traceback (most recent call last)

    File "C:\Python38\Lib\site-packages\flask\app.py", line 2464, in __call__

    return self.wsgi_app(environ, start_response)

    File "C:\Python38\Lib\site-packages\flask\app.py", line 2450, in wsgi_app

    response = self.handle_exception(e)

    File "C:\Python38\Lib\site-packages\flask\app.py", line 1867, in handle_exception

    reraise(exc_type, exc_value, tb)

    File "C:\Python38\Lib\site-packages\flask\_compat.py", line 39, in reraise

    raise value

    File "C:\Python38\Lib\site-packages\flask\app.py", line 2447, in wsgi_app

    response = self.full_dispatch_request()

    File "C:\Python38\Lib\site-packages\flask\app.py", line 1952, in full_dispatch_request

    rv = self.handle_user_exception(e)

    File "C:\Python38\Lib\site-packages\flask\app.py", line 1821, in handle_user_exception

    reraise(exc_type, exc_value, tb)

    File "C:\Python38\Lib\site-packages\flask\_compat.py", line 39, in reraise

    raise value

    File "C:\Python38\Lib\site-packages\flask\app.py", line 1950, in full_dispatch_request

    rv = self.dispatch_request()

    File "C:\Python38\Lib\site-packages\flask\app.py", line 1936, in dispatch_request

    return self.view_functions[rule.endpoint](**req.view_args)

    File "C:\school\project1\application.py", line 42, in login

    if username is not None and usernamedata[0] == username and passworddata[0] == password:

    TypeError: 'NoneType' object is not subscriptable

Here's my code in question:

@app.route("/login", methods=["GET","POST"])
def login():
    password = request.form.get("password")
    username = request.form.get("username")
    usernamedata = db.execute("SELECT username FROM users WHERE username=:username", {"username":username}).fetchone()
    passworddata = db.execute("SELECT password FROM users WHERE username=:username", {"username":username}).fetchone()
    
    if username is not None and usernamedata[0] == username and passworddata[0] == password:
        print("welcome")
        return render_template("welcome.html")
    elif username is not None and (usernamedata[0] != username or passworddata[0] != password):
        print("no match")
        return render_template("login.html")
    else:
        print("empty")
        return render_template("login.html")