Audio Visualizer - "Undefined value used in the expression(Could be out of range array subscript)"

Hi,

I am following tutorial how to make audio visualizer in After Effect but when I tried to do expressions in "offset turbulence" and I changed values to

X = effect ("Fractal Noise")("Offset Turbulence")[0];
Y=effect ("Fractal Noise")("Offset Turbulence")[1]
[X + time*50, Y]

it says "Undefined value used in the expression(Could be out of range array subscript)"

even tho I think I did everthink same as in the tutorial.

I would apreciate any ideas what to do. Thank you

link to tutorial: https://www.youtube.com/watch?v=vC6GndwmP-Q&list=RDCMUCs056Y-_0okVT4-3APWNWww&start_radio=1&t=122s