How do you fix a bug, where players heal?

There's a bug in this script, the bug is if someone is healing, and they get killed, the script will break. It's a button, where if you step on it, it will turn black, heal you, then turn back to red. When someone kills you while you're healing it'll turn black, but then it will not go back to red, and the script breaks so you can not heal with it anymore. Can somebody help me out with this bug? Here's the script:

db=false
function heal(player)


if db then return end
db=true



local h = player.Parent:FindFirstChild("Humanoid")

if h~= nil and h:FindFirstChild("Value")== nil then

local brick=script.Parent   

character=h.Parent

torso=h.Parent.Torso

if h.Health <100 then

print("Charging Heal-Pad!")

for i=1,10 do


wait(.1)    

brick.Transparency=brick.Transparency + .1





end

brick.BrickColor=BrickColor.new("Really black")
wait(.1)

for j=1,10 do

wait(.1)    

brick.Transparency=brick.Transparency - .1

end



while h.Health < 100 do


wait(.111111)
h.Health=h.Health+4


end

print("All Healed! Step off to re")

x=Instance.new("StringValue")
x.Parent=h

while true do



wait(.5)

if torso:FindFirstChild("Value") ~= nil then break end

tp=torso.Position 

bp=brick.Position


if (tp-bp).Magnitude>=5.6 then 


for _=1,10 do


wait(.1)    

brick.Transparency=brick.Transparency + .1


end

brick.BrickColor=BrickColor.new("Really red")

for s_=1,10 do


wait(.1)    

brick.Transparency=brick.Transparency - .1  

NOOBMONSTER=Instance.new("StringValue") 
NOOBMONSTER.Parent=torso

end

end

end


 es=torso:GetChildren() 

for ess=1,#es do

if es[ess].Name==("Value") then es[ess]:Destroy() end

end

x.Parent=nil
db=false return end




end




db=false




end 


script.Parent.Touched:connect(heal)