esx five m inventory string issue

Question

[enter image description here](https://i.stack.imgur.com/Sk8V7.[enter image description here](https://i.stack.imgur.com/cqnZu.png)pnenter image description hereg)

Please can some one help, i have attached 3 images of all code need for this issue

getting bad argument #1 to 'upper' (string expected, got nil) i have posted code below as well:

mf/src/client

local internalOpenWeaponLoadout = function(data)
  local k,v = ESX.GetWeapon(data.name)

  local categories = {}

  local weapon = {
    name = data.name:lower(),
    label = data.label,
    WeaponId = data.metadata.WeaponUniqueId,
    components = {}
  }

esx/commom/functions

function ESX.GetWeapon(weaponName)
    weaponName = string.upper(weaponName)

    for k,v in ipairs(Config.Weapons) do
        if v.name == weaponName then
            return k, v
        end
     end
end

I tried changing string to match weaponname 'lower'