Error: invalid argument #3 (string expected, got nil)?

I get this error: invalid argument #3 (string expected, got nil). These are the scripts:

Server script:

local rigs = game.Workspace.Rigs:GetChildren()
local event = game.ReplicatedStorage.RigTouched

for _, rig in pairs(rigs) do
	rig.OpenGuiPart.ClickDetector.MouseClick:Connect(function(player)
		local rigID = rig.ClothingID.Value
		event:FireClient(player, rigID)
	end)
end

Local script:

local event = game.ReplicatedStorage.RigTouched
local CurrentClothingID = script.Parent.ShopBackround.CurrentClothing

event.OnClientEvent:Connect(function(player, rigId)
	script.Parent.ShopBackround.Visible = true
	CurrentClothingID.Value = rigId
	print(rigId)
end)

I have read the code several times but still do not understand what is the problem. The error is on line 6 of the local script.

I see the mistake. You see, only OnServerEvent needs the player argument. OnClientEvent doesn't. So on the local script, do this instead:

local event = game.ReplicatedStorage.RigTouched
local CurrentClothingID = script.Parent.ShopBackround.CurrentClothing

event.OnClientEvent:Connect(function(rigID)
	script.Parent.ShopBackround.Visible = true
	CurrentClothingID.Value = rigId
	print(""..rigID)
end)