Error bad argument #3 to 'Text' (string expected, got nil) How do i fix?

im making a dialogue script that changes the dialogue box when an image button is clicked im getting the error in the title

while true do 
wait(0.1)
game.Players.LocalPlayer.PlayerGui.ScreenGui.Frame.ImageButton.MouseButton1Down:Connect(function()
local words = {"Test1", "Test2"}

local wordSelect = words[math.random(1, #words)]
 game.StarterGui.DialogueGui.Frame.Dialogue.Text = worldSelect
	end)
end