SWEP "shoots" through brushed

[JayTheSheep]

Hi,
I am using a SWEP for Deathrun, which unfortunaly can hit through invisible brushes/walls.
What do I do to remove that?

local tr = {}
	tr.start = self.Owner:GetShootPos()
	tr.endpos = self.Owner:GetShootPos() + ( self.Owner:GetAimVector() * 110 )
	tr.filter = self.Owner
	tr.mask = MASK_SHOT
	local trace = util.TraceLine( tr )

	self.Weapon:SetNextPrimaryFire(CurTime() + self.Primary.Delay)
	self.Owner:SetAnimation( PLAYER_ATTACK1 )

	if ( trace.Hit ) then

		if trace.Entity:IsPlayer() or string.find(trace.Entity:GetClass(),"npc") or string.find(trace.Entity:GetClass(),"prop_ragdoll") then
			self.Weapon:SendWeaponAnim(ACT_VM_HITCENTER)
			bullet = {}
			bullet.Num    = 1
			bullet.Src    = self.Owner:GetShootPos()
			bullet.Dir    = self.Owner:GetAimVector()
			bullet.Spread = Vector(0, 0, 0)
			bullet.Tracer = 0
			bullet.Force  = 1
			bullet.Damage = self.Primary.Damage
			self.Owner:FireBullets(bullet) 
			elseif string.find(trace.Entity:GetClass(),"nodraw") then
				return
			else
			self.Weapon:SendWeaponAnim(ACT_VM_HITCENTER)
			bullet = {}
			bullet.Num    = 1
			bullet.Src    = self.Owner:GetShootPos()
			bullet.Dir    = self.Owner:GetAimVector()
			bullet.Spread = Vector(0, 0, 0)
			bullet.Tracer = 0
			bullet.Force  = 1000
			bullet.Damage = self.Primary.Damage
			self.Owner:FireBullets(bullet) 
			self.Weapon:EmitSound( self.WallSound )		
			util.Decal("ManhackCut", trace.HitPos + trace.HitNormal, trace.HitPos - trace.HitNormal)
		end
	else
		self.Weapon:EmitSound(self.MissSound,75,math.random(90,120))
		self.Weapon:SendWeaponAnim(ACT_VM_MISSCENTER)
	end

I tried to use

string.find(trace.Entity:GetCollisionGroup(),"COLLISION_GROUP_PLAYER")

but it doesn't work either