My prop script keeps making an error? [UNSOLVED]

So, what I'm trying to do is make so that I can spawn a prop from my props folder/models. I've already figured out how to make it work by using server scripts, but I want to make it spawn one when I press C. Here is the my propAPIMain script inside my ServerScriptStorage. I don't need it to be FilteringEnabled right now, thats not what I'm trying to do.

--Made by dudemanjude

print '[PropAPI] Starting up.'
p = game.ServerStorage.PropAPI.Props

--This is the function I used for spawning the props with the server scripts.
_G.spawnProp = function(propName, pos)
	local prop = findProp(propName):Clone()
	print("[PropAPI] Spawning prop: " .. prop.Name)
	prop:MoveTo(pos)
	prop.Parent = workspace
end
--This function is for spawning with client scripts.
workspace.spawnProp.OnServerInvoke = function(propName, pos)
	local prop = findProp(propName):Clone()
	print("[PropAPI] Spawning prop: " .. prop.Name)
	prop:MoveTo(pos)
	prop.Parent = workspace
end

function findProp(propName)
	for i, prop in ipairs(p:GetChildren()) do
		if prop.Name == propName then
			return prop
		end
	end
end

Now here is the script for making the prop spawn when I press C. This script is inside of the StarterPack.

--Made by dudemanjude

mouse = game.Players.LocalPlayer:GetMouse()
spawnKey = "c"
cP = game.Players.LocalPlayer.Character.Torso.Position + Vector3.new( 0,10,0 )

mouse.KeyDown:connect(function( key )
	if key == spawnKey then
		workspace.spawnProp:InvokeServer("crate_01", cP)
	end
end)

The error I keep getting is this: 17:23:17.744 - ServerScriptService.propAPIMain:13: attempt to index a nil value 17:23:17.745 - Script 'Players.Player1.Backpack.crateSpawn', Line 9 17:23:17.746 - Stack End 17:23:17.746 - Disconnected event because of exception

I've tried many things, but they just won't work. Thanks, dudemanjude.