What is wrong with this Hint script?

I'm making a Hint script that should say "Currently No Map is Running" If all of the maps are nil (3) But I am having a bit of a problem

07:03:00.952 - sft is not a valid member of Workspace

I feel after that gets fixed it will go onto the next one, So I will give you all the maps

1. sft 2.gft 3.obby

Please Help if you can.

EDIT

while wait() do
local h = Instance.new("Hint")
local sftg = game.Workspace.sft
local gftg = game.Workspace.gft
local obbyg = game.Workspace.obby

if sftg == nil or gftg == nil or obbyg == nil then
h.Text = "There is Currently No Map Running"
end
end

You need to use FindFirstChild()

local v = a.b --Variable "a" exists, but "b" does not, so it breaks
local v = a:FindFirstChild('b') --Again, "b" does not exist, but it returns nil instead of breaking