Lua error [darkrp]

Hi, this is the error I got last night after installing a recent printer addon

[ERROR] addons/darkrpmodification/lua/entities/k_coolant_cell/cl_init.lua:5: Tried to use a NULL entity!

  1. GetClass - [C]:-1
  2. fn - addons/darkrpmodification/lua/entities/k_coolant_cell/cl_init.lua:5
    3. unknown - addons/ulib/lua/ulib/shared/hook.lua:183

This is the printer addon page:


Add this line above it:

if not ( IsValid( tr.Entity ) ) then return end;


Above the line that is erroring.