Attempt to call method "Fire" a nil value

[austin1346]

/*---------------------------------------------------------
   Name: Door Meta Functions
   Desc: 
---------------------------------------------------------*/

local meta = FindMetaTable("Entity")

function meta:isKeysOwnable()

	if not IsValid(self) then return false end

	local class = self:GetClass()

	if ((class == "func_door" or class == "func_door_rotating" or class == "prop_door_rotating") or
	( self:IsVehicle() and (not IsValid(self:GetParent()) or not self:GetParent():IsVehicle()))) then

			return true

		end

	return false

end

/*---------------------------------------------------------
   Name: SWEP: Functions
   Desc: 
---------------------------------------------------------*/

function SWEP:PrimaryAttack()

	if not IsFirstTimePredicted() then return end

	self:SetNextPrimaryFire( CurTime() + 0.3 )

		local tr = self:GetOwner():GetEyeTrace()
		local ent = tr.Entity

		if ent:isKeysOwnable() then

			ent:Fire( "lock" )

		end
	
end

I've copy and pasted this from my old version that worked and now it's returning an error.
Even though it throws an error it still locks the door...

Here's the error

[ERROR] gamemodes/x/entities/weapons/keys/shared.lua:107: attempt to call me
thod 'Fire' (a nil value)
  1. unknown - gamemodes/x/entities/weapons/keys/shared.lua:107