Script attached to 'Main Camera' in scene '' is missing or no valid script is attached.

I keep getting this error after the build, and it makes the camera looking messed up. There's nothing wrong with the mouse look script, and everything works fine in the unity game engine, but for some reason the build is messed up. does anyone know why this is? it all happened after I tried making a build for android, and then when I later made a windows build, it was messed up.

Thanks