Why do I get the "HeadScale is not a valid member of Model 'Workspace.(PlayerName)'" error?

I'm trying to make a player shrink, speed up, and become invisible when they touch a certain part, using a client-to-server remote event.

Here's the local script:

local player = game.Players.LocalPlayer
local char = player.Character or player.CharacterAdded:Wait()
local hum = char:WaitForChild("Humanoid")
local debounce = false
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteEvent = ReplicatedStorage:WaitForChild("RemoteEventTest")

local function inkTouched(part)
    if not debounce then
        debounce = true
        if part.Name == "Ink" then
            RemoteEvent:FireServer(player, char, hum)
            print("Client communicating with server...")
        end
    end
    debounce = false
end

hum.Touched:Connect(inkTouched)

And here's the server script:

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteEvent = ReplicatedStorage:WaitForChild("RemoteEventTest")

local function inkTouched(player, char, hum)
    hum.HeadScale = 0.05
    hum.BodyDepthScale = 0.05
    hum.BodyWidthScale = 0.05
    hum.BodyHeightScale = 0.05
    hum.WalkSpeed = 32
    for _, item in pairs(char:GetChildren()) do
        if item:IsA("BasePart") then
            item.Transparency = 1
        end
    end
    print("Communication successful!")
end

RemoteEvent.OnServerEvent:Connect(inkTouched)

When I run the game, the remote event itself worked but I get this error: "HeadScale is not a valid member of Model 'Workspace.Isocyanic'". Why?