Null Reference exception when messing with AudioListener.volume with slider

Whenever I run my game there is a null reference exception being called every frame on line 33 of my code here: null reference exception line 33 -

I’m wondering how I can stop this error being logged every frame since I find it kind of annoying, I know it’s being called every frame because it is in the update function, and that it is asking for an instance of audiolistener but the volume variable is static so I’m not sure how to make it so that the error is fixed. I also wouldn’t mind if the error isn’t technically fixed but the error just stops logging.

I fixed all my errors after realizing I had to add the relevant objects in the inspector into the menu script component’s slots for every object that had the menu script component. Because I figured since my slider obviously doesn’t have anything to do with my play or options or quit buttons & canvases. I didn’t have to add it in. I had to do this for every object that had the menu script component.