How Do I fix Argument 1 Missing or nil?

First of all I just wan't to say This is the first Time I'm using Remotes, Anyway I'm trying to get this remote to give me hits when Triggered.

If you need more info please reply.

The Remote:

game.ReplicatedStorage.Remotes.AddHit.OnServerEvent:Connect(function()
	local plr = game:GetService("Players").LocalPlayer
	local hits = plr:WaitForChild("Hits")
	hits.Value = hits.Value + 10
end)

Script: (LINE 227 - 229)

--Rescripted by Luckymaxer
bf = game.ReplicatedStorage.Remotes.AddHit
bff = game.ReplicatedStorage.Remotes.AddHitBasic
Tool = script.Parent
Handle = Tool:WaitForChild("Handle")

Players = game:GetService("Players")
Debris = game:GetService("Debris")

Speed = 50
Duration = 1

NozzleOffset = Vector3.new(0, 0.4, -1.1)

Sounds = {
	Fire = Handle:WaitForChild("Fire"),
	Reload = Handle:WaitForChild("Reload"),
	HitFade = Handle:WaitForChild("HitFade")
}

PointLight = Handle:WaitForChild("PointLight")

ServerControl = (Tool:FindFirstChild("ServerControl") or Instance.new("RemoteFunction"))
ServerControl.Name = "ServerControl"
ServerControl.Parent = Tool

ClientControl = (Tool:FindFirstChild("ClientControl") or Instance.new("RemoteFunction"))
ClientControl.Name = "ClientControl"
ClientControl.Parent = Tool

ServerControl.OnServerInvoke = (function(player, Mode, Value, arg)
	if player ~= Player or Humanoid.Health == 0 or not Tool.Enabled then
		return
	end
	if Mode == "Click" and Value then
		Activated(arg)
	end
end)

function InvokeClient(Mode, Value)
	pcall(function()
		ClientControl:InvokeClient(Player, Mode, Value)
	end)
end

function TagHumanoid(humanoid, player)
	local Creator_Tag = Instance.new("ObjectValue")
	Creator_Tag.Name = "creator"
	Creator_Tag.Value = player
	Debris:AddItem(Creator_Tag, 2)
	Creator_Tag.Parent = humanoid
end

function UntagHumanoid(humanoid)
	for i, v in pairs(humanoid:GetChildren()) do
		if v:IsA("ObjectValue") and v.Name == "creator" then
			v:Destroy()
		end
	end
end

function FindCharacterAncestor(Parent)
	if Parent and Parent ~= game:GetService("Workspace") then
		local humanoid = Parent:FindFirstChild("Humanoid")
		if humanoid then
			return Parent, humanoid
		else
			return FindCharacterAncestor(Parent.Parent)
		end
	end
	return nil
end

function GetTransparentsRecursive(Parent, PartsTable)
	local PartsTable = (PartsTable or {})
	for i, v in pairs(Parent:GetChildren()) do
		local TransparencyExists = false
		pcall(function()
			local Transparency = v["Transparency"]
			if Transparency then
				TransparencyExists = true
			end
		end)
		if TransparencyExists then
			table.insert(PartsTable, v)
		end
		GetTransparentsRecursive(v, PartsTable)
	end
	return PartsTable
end

function SelectionBoxify(Object)
	local SelectionBox = Instance.new("SelectionBox")
	SelectionBox.Adornee = Object
	SelectionBox.Color = BrickColor.new("Really red")
	SelectionBox.Parent = Object
	return SelectionBox
end

local function Light(Object)
	local Light = PointLight:Clone()
	Light.Range = (Light.Range + 2)
	Light.Parent = Object
end

function FadeOutObjects(Objects, FadeIncrement)
	repeat
		local LastObject = nil
		for i, v in pairs(Objects) do
			v.Transparency = (v.Transparency + FadeIncrement)
			LastObject = v
		end
		wait()
	until LastObject.Transparency >= 1 or not LastObject
end

function Dematerialize(character, humanoid, FirstPart)
	if not character or not humanoid then
		return
	end
	
	humanoid.WalkSpeed = 0

	local Parts = {}
	
	for i, v in pairs(character:GetChildren()) do
		if v:IsA("BasePart") then
			v.Anchored = true
			table.insert(Parts, v)
		elseif v:IsA("LocalScript") or v:IsA("Script") then
			v:Destroy()
		end
	end

	local SelectionBoxes = {}

	local FirstSelectionBox = SelectionBoxify(FirstPart)
	Light(FirstPart)
	wait(0.05)

	for i, v in pairs(Parts) do
		if v ~= FirstPart then
			table.insert(SelectionBoxes, SelectionBoxify(v))
			Light(v)
		end
	end

	local ObjectsWithTransparency = GetTransparentsRecursive(character)
	FadeOutObjects(ObjectsWithTransparency, 0.1)

	wait(0.5)

	character:BreakJoints()
	humanoid.Health = 0
	
	Debris:AddItem(character, 2)

	local FadeIncrement = 0.05
	Delay(0.2, function()
		FadeOutObjects({FirstSelectionBox}, FadeIncrement)
		if character and character.Parent then
			character:Destroy()
		end
	end)
	FadeOutObjects(SelectionBoxes, FadeIncrement)
end

function Touched(Projectile, Hit)
	if not Hit or not Hit.Parent then
		return
	end
	local character, humanoid = FindCharacterAncestor(Hit)
	if character and humanoid and character ~= Character then
		local ForceFieldExists = false
		for i, v in pairs(character:GetChildren()) do
			if v:IsA("ForceField") then
				ForceFieldExists = true
			end
		end
		if not ForceFieldExists then
			if Projectile then
				local HitFadeSound = Projectile:FindFirstChild(Sounds.HitFade.Name)
				local torso = humanoid.Torso
				if HitFadeSound and torso then
					HitFadeSound.Parent = torso
					HitFadeSound:Play()
				end
			end
			Dematerialize(character, humanoid, Hit)
		end
		if Projectile and Projectile.Parent then
			Projectile:Destroy()
		end
	end
end

function Equipped()
	Character = Tool.Parent
	Player = Players:GetPlayerFromCharacter(Character)
	Humanoid = Character:FindFirstChild("Humanoid")
	if not Player or not Humanoid or Humanoid.Health == 0 then
		return
	end
end

function Activated(target)
	if Tool.Enabled and Humanoid.Health > 0 then
		Tool.Enabled = false

		InvokeClient("PlaySound", Sounds.Fire)

		local HandleCFrame = Handle.CFrame
		local FiringPoint = HandleCFrame.p + HandleCFrame:vectorToWorldSpace(NozzleOffset)
		local ShotCFrame = CFrame.new(FiringPoint, target)

		local LaserShotClone = BaseShot:Clone()
		LaserShotClone.CFrame = ShotCFrame + (ShotCFrame.lookVector * (BaseShot.Size.Z / 2))
		local BodyVelocity = Instance.new("BodyVelocity")
		BodyVelocity.velocity = ShotCFrame.lookVector * Speed
		BodyVelocity.Parent = LaserShotClone
		LaserShotClone.Touched:connect(function(Hit)
			if not Hit or not Hit.Parent then
				return
			end
			Touched(LaserShotClone, Hit)
			if Hit.Parent:FindFirstChild("Humanoid") then
			bf:FireClient()
			else
			bff:FireClient()
			end
		end)
		Debris:AddItem(LaserShotClone, Duration)
		LaserShotClone.Parent = game:GetService("Workspace")
		wait(0.6) -- FireSound length

		InvokeClient("PlaySound", Sounds.Reload)
		
		wait(0.75) -- ReloadSound length

		Tool.Enabled = true
	end
end

function Unequipped()
	
end

BaseShot = Instance.new("Part")
BaseShot.Name = "Effect"
BaseShot.BrickColor = BrickColor.new("Really red")
BaseShot.Material = Enum.Material.Plastic
BaseShot.Shape = Enum.PartType.Block
BaseShot.TopSurface = Enum.SurfaceType.Smooth
BaseShot.BottomSurface = Enum.SurfaceType.Smooth
BaseShot.FormFactor = Enum.FormFactor.Custom
BaseShot.Size = Vector3.new(0.2, 0.2, 3)
BaseShot.CanCollide = false
BaseShot.Locked = true
SelectionBoxify(BaseShot)
Light(BaseShot)
BaseShotSound = Sounds.HitFade:Clone()
BaseShotSound.Parent = BaseShot

Tool.Equipped:connect(Equipped)
Tool.Unequipped:connect(Unequipped)

The Error: Argument 1 missing or nil

When you fire a client, you must specify WHICH client you wanna fire with the client's name (basically the player).

You can do bf:FireClient(GetPlayerFromCharacter(hit.Parent)

Your "missing argument" is the player. On serverside, whether its firing to the client or from the client, the first argument must always be the player. Name it what you want but you MUST have some kind of variable as the first argument.

game.ReplicatedStorage.Remotes.AddHit.OnServerEvent:Connect(function(player, arg1, arg2)
	--code
end)