TTT Lua Traitorhop dosent works

I want to load some weapon addons on my TTT Serever but now i have a problem with the Traitorshop, because if i equip the weapon and i am traitor and i press C to open the tshop i get a grew window at the bottom is written equipment but i didnt see anything. I get this Error
[ERROR] gamemodes/terrortown/gamemode/cl_equip.lua:397: attempt to call method ‘IsEquipment’ (a nil value)

  1. unknown - gamemodes/terrortown/gamemode/cl_equip.lua:397
  2. unknown - lua/includes/modules/concommand.lua:54

Can sombody help me i tried to googel it i didn’t find the error.
and i lookt up the cl_equip.lua in this line 397 is nothing.