[Bug] lib.class private table returns not expected value

[deFuzz77]

Describe the bug
I have problem with private table in lib.class, acctualy when I call method from the same method, the private table returns null.

To Reproduce
I wrote simple code to reproduce this.

local Inventory = lib.class('Inventory')

function Inventory:constructor()
    self.private.items = { { name = 'bread', count = 1 }, { name = 'water', count = 2 } }
end

function Inventory:getItem(rec)
    print(json.encode(self.private.items))
    rec = rec or 0
    if rec == 1 then return end
    rec += 1
    return self:getItem(rec)
end

local playerInventory = Inventory:new()
playerInventory:getItem()

--[[
    returns:
        --> [{"count":1,"name":"bread"},{"count":2,"name":"water"}]
        --> null
]]

Expected behavior
I expected the private table return its data.