problem with broken addon

Hey
Today I installed broken addon to my server to try if its working (Last addon update something like 5/4 years ago)
Soo I tryed to fix the addon but I could not
The code is (its the cl_nametags.lua)

Console error
[ERROR] addons/nametags/lua/autorun/client/cl_nametags.lua:21: table index is nil

  1. Function - addons/nametags/lua/autorun/client/cl_nametags.lua:21
  2. unknown - lua/includes/modules/usermessage.lua:87

[ERROR] addons/nametags/lua/autorun/client/cl_nametags.lua:21: table index is nil

  1. Function - addons/nametags/lua/autorun/client/cl_nametags.lua:21
  2. unknown - lua/includes/modules/usermessage.lua:87

I will very happy if someone will fix the code for me
(IM SORRY I mistakenly opened the topic on Garry’s Mod General Discussion and not on Help & Support my bad)