Attempt to index local 'Humanoid'(A nil value)?

I am trying to make an idle animation stop but when I put in Character:FindFirstChild("Humanoid") it says "20:48:14.460 - Players.360gamer107.Backpack.Desteller.LocalScript:72: attempt to index local 'Humanoid' (a nil value)" The problem is on lines 69 - 77.

local debounce = false								  
local Tool     = script.Parent						  
local Handle   = Tool:WaitForChild("Handle")		  
ValueCooldown  = false								  

function SwordCore(hit)															
	local Enemys = hit.Parent:FindFirstChildOfClass("Humanoid")					
	if script.CanDamage.Value and Enemys then						  		 	
		local EnemyHit = hit.Parent:FindFirstChild("Enemy")						
		local PlayerHit = hit.Parent:FindFirstChild("Humanoid")					
		local Character = Tool.Parent											
		local Player = game.Players:GetPlayerFromCharacter(Character)			
		if (not Player) then return end											
		local Humanoid = Character:FindFirstChild("Humanoid")					
		if (not Humanoid) then return end										
		if Enemys ~= Humanoid and (not debounce) then							
			if Enemys.Health <= 0 then return end								 
			debounce = true														
			if PlayerHit then													
				game.ReplicatedStorage.PlayerHit:FireServer(hit,PlayerHit,Tool)	
			end																	
			if EnemyHit then													
				game.ReplicatedStorage.EnemyHit:FireServer(hit,EnemyHit,Tool)	
			end																	
			wait(1)																
			debounce = false													
		end																		
	end																			
end																				
local on = 1
local timer = tick()
function onActivated()										
	if (not Tool.Enabled) then return end					
	Tool.Enabled = false									
	if tick()-timer >2 then
		on = 1
	end		
	timer = tick()							
	local Character = Tool.Parent								
	local Humanoid = Character:FindFirstChild("Humanoid")	
	local Anim = Humanoid:LoadAnimation(Tool["Slash".. on]) 
	local SlashSound = Handle:WaitForChild("SlashSound")	
	if (Humanoid == nil) then return end					
	SlashSound:Play()										
	Anim:Play()												
	Tool.Unequipped:Connect(function()						
		Anim:Stop()											
	end)													
	on = on + 1
	if on >= 4 then
		on = 1
	end
	wait(0.5)													
	Tool.Enabled = true										
end

function onEquipped()
	local Character = Tool.Parent								
	local Humanoid = Character:FindFirstChild("Humanoid")	
	local Idle = Humanoid:LoadAnimation(Tool.Idle)
	if (not Tool) then return end
	if (not Handle) then return end
	Idle:Play()
	if Handle.UnsheathSound.IsPlaying == false then
		Handle.UnsheathSound:Play()
	end
end	

function onUnEquipped()
	local Character = Tool.Parent								
	local Humanoid = Character:FindFirstChild("Humanoid")	
	local Idle = Humanoid:LoadAnimation(Tool.Idle)
	if (not Tool) then return end
	if (not Handle) then return end
	Idle:Stop()
	Handle.UnsheathSound:Stop()
end


function checkValue()
	if ValueCooldown           == false then
		ValueCooldown          = true
		script.CanDamage.Value = true
		wait(1)
		script.CanDamage.Value = false
		ValueCooldown          = false
	end
end

Tool.Activated:Connect(onActivated) 
Tool.Activated:Connect(checkValue)	
Tool.Equipped:Connect(onEquipped)   
Tool.Unequipped:Connect(onUnEquipped) 

Handle.Touched:Connect(SwordCore)   ``

The reason for this error is that once the Tool is unequipped, it is no longer part of the player's character, but rather their Backpack. Because it is now a member of the backpack, and there is no object named "Humanoid" in the backpack, FindFirstChild returns nil, and your attempt to index nil throws an error on line 72.

To solve this, you need to access the player's character through other means, the best being Player.Character.

Lines 69-77 Revised:

function onUnEquipped()
    local Backpack = Tool.Parent;
    local Player = Backpack.Parent;
    local Character = Player.Character;                               
    local Humanoid = Character:FindFirstChild("Humanoid")   
    local Idle = Humanoid:LoadAnimation(Tool.Idle)
    if (not Tool) then return end
    if (not Handle) then return end
    Idle:Stop()
    Handle.UnsheathSound:Stop()
end