My anti-fly exploit is not working and is claiming that "HumanoidRootPart" is not in the player?

-------------------------------
--random name
math.randomseed(os.time())
for i = 1,157 do

local name = math.random()
script.Name = name
end
--so hackers cant delete the script
--------------------------------

local plr = game.Players.LocalPlayer
local bp = plr.Backpack
local char = plr.Character


--Fly
char.HumanoidRootPart.ChildAdded:connect(function(l)
    if l.ClassName ~= "BodyGyro" then
        plr:Kick("Fly Hacking")
    end
end)

char.UpperTorso.ChildAdded:connect(function(l)
    if l.ClassName ~= "BodyGyro" then
        plr:Kick("Fly Hacking")
    end
end)

char.LowerTorso.ChildAdded:connect(function(l)
    if l.ClassName ~= "BodyGyro" then
        plr:Kick("Fly Hacking")
    end
end)

This script was to kick players who are fly hacking, but I keep getting "HumanoidRootPart is not in model" in console? Any fixes?