client side mod help, Hide Overlay

All i need my mod to do is hide Overlay elements like healthbar etc.
So i created a mod with just this one custom element:

https://pastebin.com/embed_js/tLN2Bn5M

This works in singelplayer.

I want this to work on a multiplayer server.

The problem is, that when i put this mod on a server it will crash on startup and give me the error 

https://pastebin.com/S5Hn3RSu

If i put it on only the client it wont let me join because the mod is missing on the server side.
So i either need a way to make this a client side only mod that wont complain when its not on the server, or i need it to be able to start on the server without issues.
Is there any other way simpler way to do what my mod does without causing any issues?