Need help with my thirst script. Roblox Studio Crashes. why?

Hey there! I am a bit new to scripting and I've been trying to make a thirst script. Here's how it is so far:

Thirst = 100
player = game.Players.LocalPlayer.Character

if Thirst <= 50 then
    game.Players.LocalPlayer.PlayerGui.ThirstWarn.Thirst2.Visible = true else
    game.Players.LocalPlayer.PlayerGui.ThirstWarn.Thirst2.Visible = false
end


while Thirst > 0 do
wait(2)
Thirst = Thirst - 10
end

while Thirst == 0 do
    wait(2)
    player.Humanoid.Health = player.Humanoid.Health - 10
end

It was going well, the thirst would decrease and then the health would start decreasing aswell. But I wanted to make it better. So I added a GUI with the following text: "You are thirsty!". I wanted this GUI to appear when the thirst was below 50. To do that I made this:

if Thirst <= 50 then
    game.Players.LocalPlayer.PlayerGui.ThirstWarn.Thirst2.Visible = true else
    game.Players.LocalPlayer.PlayerGui.ThirstWarn.Thirst2.Visible = false
end

But whenever I try to run the game, it just crashes. What's wrong? D: