Face Changing GUI isn't working? - attempt to index nil with 'Character' error

Hello, I need some help. I'm trying to make a face changing GUI where, when the player clicks the Image Button in the GUI, their avatar's face will change to match the image they clicked.

This is what I got so far:

function applyFace(plr)
	    local h = plr.Character:findFirstChild("Head")
        if h~=nil then
        h.face.Texture = script.Parent.Image
    end
end

script.Parent.MouseButton1Click:Connect(applyFace)

For some reason, when I click on the face button, the output windows says "attempt to index nil with Character". Any idea on how to fix it?

Make sure to add on line 2 or plr.CharacterAdded:Wait()

Here is an example

function applyFace(plr)
        local h = plr.Character:findFirstChild("Head") or plr.CharacterAdded:Wait()
        if h~=nil then
        h.face.Texture = script.Parent.Image
    end
end

script.Parent.MouseButton1Click:Connect(applyFace)

Also check if you put your script as a local script in a StarterGui