Error "Tried to use a NULL entity!"

[Rayek]

I have a weapon problem for TTT mode, I have a "weapon_ttt_ied" addon on the server, it usually works without a problem, but once every few days I have 18k logs for no reason:
[ERROR] addons/ttt_ied/lua/autorun/sh_ied.lua:45: Tried to use a NULL entity!
  1. GetPos - [C]:-1
   2. fn - addons/ttt_ied/lua/autorun/sh_ied.lua:45
    3. unknown - addons/ulx_ulib_v2.63/lua/ulib/shared/hook.lua:109

Here I am sending a file to download, could anyone help me solve this problem?
sh_ied.lua

[joeyjumper]

did you make this yourself?
are there multiple people using this at the same time?
try changing this function
function ENT:doIEDExplosionThink( ply, snd, wep, delay )
    local delay = delay or CurTime() + 3.2

    self.detonating = true
    self.timeUntilDet = delay

    if SERVER then
        hook.Add( "Think", "IEDExplosion"..self:EntIndex(), function()
if !self or self and !self:IsValid() then return end--let's make sufe the entity is not NULL before we proceed

            if CurTime() > delay then
                self.timeUntilDet = delay - CurTime()
                if !self:IsPlayer() or self:Alive() then
                    self.detonating = false
                    util.BlastDamage( Entity( 0 ), ply and ply or Entity( 0 ), self:GetPos(), 800, 200 )

                    local effect = EffectData()
                    effect:SetStart( self:GetPos() )
                    effect:SetOrigin( self:GetPos() )
                    effect:SetScale( 400 )
                    effect:SetRadius( 400 )
                    effect:SetMagnitude(220 )
                    effect:SetNormal( self:GetUp() )
                    util.Effect("Explosion", effect, true, true)

                    hook.Remove( "Think", "IEDExplosion"..self:EntIndex() )

                    ply:setIEDTarget( nil )
                    self:setIED( false )

                else

                    hook.Remove( "Think", "IEDExplosion"..self:EntIndex() )

                end

            end

        end)
    end
end

[Grocel]

Use IsValid(self). It checks if self is not nil and if it is valid.
Remember when using timers or hooks with asynchronous functions (functions that are not executed in the same frame), the entity could be removed in between. So always use IsValid checks in said functions.