I am creating an app which is just an TOTP authenticicator (sorry if spelt wrong)

But for some reason, my app started throwing an error TypeError: 'NoneType' object is not subscriptable

I dont really know the issue though, but i tried to change all spaces to tabs, didnt work.

And heres the almost full error, and code.

Error:

File "/data/user/0/ru.iiec.pydroid3/files/aarch64-linux-android/lib/python3.11/site-packages/kivy/lang/parser.py", line 696, in parse_level
     _objects, _lines = self.parse_level(
                        ^^^^^^^^^^^^^^^^^
   File "/data/user/0/ru.iiec.pydroid3/files/aarch64-linux-android/lib/python3.11/site-packages/kivy/lang/parser.py", line 756, in parse_level
     if current_property[:3] == 'on_':
        ~~~~~~~~~~~~~~~~^^^^
 TypeError: 'NoneType' object is not subscriptable

And code:

import hmac


import base64


import struct
import hashlib
import time
import plyer

import pickle


def get_hotp_token(secret, intervals_no):
    key = base64.b32decode(secret, True)
    msg = struct.pack(">Q", intervals_no)
    h = hmac.new(key, msg, hashlib.sha1).digest()
    o = h[19] & 15
    h = (struct.unpack(">I", h[o:o+4])[0] & 0x7fffffff) % 1000000
    return h
 
from kivymd.app import MDApp 

from kivymd.uix.boxlayout import MDBoxLayout
 
from kivy.lang import Builder 
 
class auther(MDApp):  
    def build(self): 
        return Builder.load_string("""
<DrawerClickableItem@MDNavigationDrawerItem>
    focus_color: "#e7e4c0"
    text_color: "#4a4939"
    icon_color: "#4a4939"
    ripple_color: "#c5bdd2"
    selected_color: "#0c6c4d"


<DrawerLabelItem@MDNavigationDrawerItem>
    text_color: "#4a4939"
    icon_color: "#4a4939"
    focus_behavior: False
    selected_color: "#4a4939"
    _no_ripple_effect: True
MDBoxLayout: 
    orientation: "vertical"
    pos: 0,0
    size_hint: 1,1
    spacing: "12dp"
    MDTopAppBar:
        title: "MDTopAppBar"
        left_action_items: [["menu", lambda x: nav_drawer.set_state("open")]]
    MDScreenManager:
        MDScreen:
            MDScrollView:
                MDRectangleFlatIconButton:
                    text: "Hello!"
                    icon: "key"
                    size_hint: 1,0.1
    MDNavigationDrawer:
        id: nav_drawer
            radius: (0, 16, 16, 0)
            MDNavigationDrawerMenu:
                MDNavigationDrawerHeader:
                    title: "Auther"
                    title_color: "#4a4939"
                    text: "Built by simpleuserdontwatch ;)"
                    spacing: "4dp"
                    padding: "12dp", 0, 0, "56dp"

                DrawerClickableItem:
                    icon: "settings"
                    text_right_color: "#4a4939"
                    text: "Settings"
""") 
 
auther().run()