Did you try to modify this add-on?
You could try quitting gmod, unsubscribing, make sure the add-on files have been removed from "\Steam\steamapps\workshop\content\4000\3323803627" (the folder "3323803627" might even be removed) then resubscribe and restart Gmod.

I've had a play with it locally and I can't get your issue to reproduce.

What are the steps leading up to the error?

i off all my addons and it s not work

Thanks for flagging!
This add-on has been working fine for my friends and I on our server but I can take a look to see if I can recreate the issue.
Do you remember what you were doing at the time the error occurred?

[Moonigun] lua/weapons/moonigun/shared.lua:134: attempt to call method 'GetPrimaryCone' (a nil value)
1. AutoAttack - lua/weapons/moonigun/shared.lua:134
2. unknown - lua/weapons/moonigun/shared.lua:105

not work