It doesn't work

[TheJ0lly]

I copy pasted the code and it fails

Traceback (most recent call last):
File "/home/thejolly/Desktop/Python/PMD/main.py", line 71, in
PongApp().run()
File "/home/thejolly/.local/lib/python3.10/site-packages/kivy/app.py", line 954, in run
self._run_prepare()
File "/home/thejolly/.local/lib/python3.10/site-packages/kivy/app.py", line 924, in _run_prepare
root = self.build()
File "/home/thejolly/Desktop/Python/PMD/main.py", line 66, in build
game.serve_ball()
File "/home/thejolly/Desktop/Python/PMD/main.py", line 35, in serve_ball
self.ball.velocity = Vector(4, 0).rotate(randint(0, 360))
AttributeError: 'NoneType' object has no attribute 'velocity'

this is the error log