'A nil value'?

I made a local script that changes your jump power based on your character's walkspeed, which works in Studio Solo Mode, however in game it gives me the error: Players.JJ_B.Backpack.jump:6: attempt to index local 'h' (a nil value) I've had this sort of problem before but I don't know how to rectify it in the context of this script. Here is the code:

while true do
local Player = game:GetService("Players").LocalPlayer
local Char = Player.Character or Player.CharacterAdded:wait()
local h = Player.Character:FindFirstChild("Humanoid")
		if h.WalkSpeed == 16 then
 			h.JumpPower = 50
		elseif h.WalkSpeed >= 16 and h.WalkSpeed <= 267 then
			h.JumpPower = 100
		elseif h.WalkSpeed >= 268 and h.WalkSpeed <= 514 then
			h.JumpPower = 150
		elseif h.WalkSpeed >= 515 and h.WalkSpeed <= 767 then
			h.JumpPower = 175
		elseif h.WalkSpeed > 767 and h.WalkSpeed <= 1000 then
			h.JumpPower = 200
		elseif h.WalkSpeed > 1000 then
			h.JumpPower = 250
		end
		wait(0.5)
		end

Help please? ;-;

You're not waiting for the Humanoid to load!

When defining variables, it's often appropriate, or necessary, to use WaitForChild.

The very simple fix would be the following.

while true do
	local Player = game:GetService("Players").LocalPlayer
	local Char = Player.Character or Player.CharacterAdded:wait()
	local h = Char:WaitForChild("Humanoid")-- Added WaitForChild
	if h.WalkSpeed == 16 then
		h.JumpPower = 50
	elseif h.WalkSpeed >= 16 and h.WalkSpeed <= 267 then
		h.JumpPower = 100
	elseif h.WalkSpeed >= 268 and h.WalkSpeed <= 514 then
		h.JumpPower = 150
	elseif h.WalkSpeed >= 515 and h.WalkSpeed <= 767 then
		h.JumpPower = 175
	elseif h.WalkSpeed > 767 and h.WalkSpeed <= 1000 then
		h.JumpPower = 200
	elseif h.WalkSpeed > 1000 then
		h.JumpPower = 250
	end
	wait(0.5)
end

I also could offer some advice to make your script more efficient.

Move your variables outside the loop, so they don't cause lag from repeatedly being created.

local Player = game:GetService("Players").LocalPlayer
local Char = Player.Character or Player.CharacterAdded:wait()
local h = Char:WaitForChild("Humanoid")

while wait(0.5) do
	if h.WalkSpeed == 16 then
		h.JumpPower = 50
	elseif h.WalkSpeed >= 16 and h.WalkSpeed <= 267 then
		h.JumpPower = 100
	elseif h.WalkSpeed >= 268 and h.WalkSpeed <= 514 then
		h.JumpPower = 150
	elseif h.WalkSpeed >= 515 and h.WalkSpeed <= 767 then
		h.JumpPower = 175
	elseif h.WalkSpeed > 767 and h.WalkSpeed <= 1000 then
		h.JumpPower = 200
	elseif h.WalkSpeed > 1000 then
		h.JumpPower = 250
	end
end

I moved the variables and moved the wait to the while loop. I also used the char variable you made but didn't use for some reason.

I hope I helped!

Good Luck!