Null entity ? :P

[GorkemF]

so here's the error that changes the playermodel of someone to a dog (the swep code is below)
[ERROR] lua/weapons/animagus swep/shared.lua:391: Tried to use a NULL entity!
  1. LookupSequence - [C]:-1
   2. MorphToHuman - lua/weapons/animagus swep/shared.lua:391
    3. unknown - lua/weapons/animagus swep/shared.lua:153
The code for the swep

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if( SERVER ) then

    AddCSLuaFile("shared.lua")

end

SWEP.Base               = "weapon_base"

SWEP.Spawnable          = true

SWEP.AdminSpawnable     = true

SWEP.ViewModel      = "models/weapons/c_arms_citizen.mdl"

SWEP.WorldModel     = ""   

SWEP.ViewModelFlip  = false

SWEP.DrawCrosshair  = false

SWEP.Primary                = {}   

SWEP.Primary.Damage         = 0                              

SWEP.Primary.ClipSize       = -1       

SWEP.Primary.Delay          = 0.5    

SWEP.Primary.DefaultClip    = 1      

SWEP.Primary.Automatic      = false       

SWEP.Primary.Ammo           = "none"     

SWEP.Secondary              = {}

SWEP.Secondary.ClipSize     = -1           

SWEP.Secondary.DefaultClip  = -1

SWEP.Secondary.Delay        = 2

SWEP.Secondary.Damage       = 0      

SWEP.Secondary.Automatic    = false      

SWEP.Secondary.Ammo         = "none"

SWEP.ReloadDelay    = 0

SWEP.AnimDelay      = 0

SWEP.AttackAnims    = {

    "fists_left",

    "fists_right"}

SWEP.PlayerModel    = nil

SWEP.WerewolfModel  = "models/jwk987/animal/riley.mdl"

SWEP.PlayerScale    = 1.0

SWEP.WerewolfScale  = 1.15 --Change the collision type of the werewolf

SWEP.HealthBonus    = 100

SWEP.HealAmount     = 1

SWEP.HealTimer      = 1

SWEP.HealId         = ""

SWEP.RunSpeed       = 500

SWEP.WalkSpeed      = 250

SWEP.SpeedModifier  = 1.0

SWEP.InfectChance   = 0.25

SWEP.InfectDuration = 12 -- 5 x 12 = 60 seconds until infection turns to werewolfisms

SWEP.ToggleVFX      = false

if ( CLIENT ) then

    SWEP.PrintName  = "Animagus Kopek"     

    SWEP.Category   = "Kuzgun HogwartsRP"

    SWEP.Author     = "Lucifer Morningstar"

    SWEP.Purpose    = "Bu yetenek ile köpek şeklini alabilirsin!"

    SWEP.Slot       = 0                  

    SWEP.SlotPos    = 1

    SWEP.DrawAmmo   = false

end

function SWEP:Equip(owner)

    self:RegeneratingHealth(owner)

    timer.Simple(0.5, function()

        if !IsValid(self) then return end

        owner:SetActiveWeapon(self)

    end)

end

function SWEP:Holster()

    local owner = self.Owner

    if owner != nil then

        self:MorphToHuman()

    end

    return true

end

function SWEP:OnRemove()

    self:RemoveSelf()

    return true

end

function SWEP:OnDrop()

    self:RemoveSelf()

    return true

end

function SWEP:RemoveSelf()

    local owner = self.Owner

    if owner != nil then

        self:MorphToHuman()

    end

    if !SERVER then return end

    if timer.Exists(self.HealId) then timer.Remove( self.HealId ) return end

    self:Remove()

end

function SWEP:Reload()

    if self.ReloadDelay > CurTime() then return end

    if self.PlayerModel == nil then return end

    self.ReloadDelay = CurTime() + 4

    self.Weapon:SetNextPrimaryFire( CurTime() + 2.5 )

    self.Weapon:SetNextSecondaryFire( CurTime() + 2.5 )

    if game.MaxPlayers() < 2 then self.AnimDelay = CurTime() + 4

    else self.AnimDelay = SysTime() + 4 end

    local owner = self.Owner

    if !owner:IsValid() then return end

    if !owner:Alive() then return end

    if owner:GetModel() != self.WerewolfModel

    then self:MorphToWerewolf()

    else self:MorphToHuman()

    end

end

function SWEP:SecondaryAttack()

    self.Weapon:SetNextSecondaryFire( CurTime() + self.Secondary.Delay )

    if game.MaxPlayers() < 2 then self.AnimDelay = CurTime() + 0.45

    else self.AnimDelay = SysTime() + 0.4 end

    local owner = self.Owner

    if !owner:IsValid() then return end

    if !owner:Alive() then return end

    if owner:GetModel() == self.PlayerModel then

        self:Reload()

return 

end

end

function SWEP:PrimaryAttack()

    self.Weapon:SetNextPrimaryFire( CurTime() + self.Primary.Delay )

    if game.MaxPlayers() < 2 then self.AnimDelay = CurTime() + self.Primary.Delay

    else self.AnimDelay = SysTime() + self.Primary.Delay end

    local owner = self.Owner

    if !owner:IsValid() then return end

    if !owner:Alive() then return end

    if owner:GetModel() == self.PlayerModel then return end

end

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function SWEP:MorphToWerewolf()

    local owner = self.Owner

    if self.PlayerModel == nil then return end

    if owner:GetModel() == self.WerewolfModel then return end

    owner:SetModelScale( self.WerewolfScale, 3 )

    owner:SetModel( self.WerewolfModel )

    if self.WerewolfScale > 1 then owner:SetCollisionGroup( COLLISION_GROUP_PASSABLE_DOOR )

    else owner:SetCollisionGroup( COLLISION_GROUP_NONE ) end

    if !owner:IsValid() then return end

    if !owner:Alive() then return end

    self:SetHoldType( "knife" )

    self:SendWeaponAnim(ACT_HL2MP_IDLE_KNIFE)

    local vm = self.Owner:GetViewModel()

    vm:ResetSequence( vm:LookupSequence( "fists_draw" ) )

end

function SWEP:MorphToHuman()

    local owner = self.Owner

    if owner == nil or !IsValid(self) then return end

    if owner:GetModel() == self.PlayerModel then return end

    owner:SetModelScale( self.PlayerScale, 3 )

    if self.PlayerModel != nil then owner:SetModel( self.PlayerModel ) end

    if self.PlayerScale > 1 then owner:SetCollisionGroup( COLLISION_GROUP_PASSABLE_DOOR )

    else owner:SetCollisionGroup( COLLISION_GROUP_NONE ) end

    owner:SetRunSpeed(self.WalkSpeed)

    owner:SetWalkSpeed(self.RunSpeed)

    if !owner:IsValid() then return end

    if !owner:Alive() then return end

    self:SetHoldType( "normal" )

    self:SendWeaponAnim(ACT_HL2MP_IDLE_KNIFE)

    local vm = self.Owner:GetViewModel()

    if CLIENT then vm:ResetSequence( vm:LookupSequence( "fists_idle_0" .. math.random( 1, 2 ) ) ) end

    vm:ResetSequence( vm:LookupSequence( "fists_holster" ) )

end

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function SWEP:RegeneratingHealth(owner)

    local hp, maxhp

    self.HealId  = math.random(165, 73623)

    self.HealId = "EOTI_WEREWOLF_SWEP_"..self.HealId..owner:Name()

    timer.Create(self.HealId , self.HealTimer, 0, function()

        if !SERVER

        or !self:IsValid()

        or !timer.Exists( self.HealId )

        then return end

        hp = owner:Health()

        maxhp = (owner:GetMaxHealth() + self.HealthBonus or 100 + self.HealthBonus)

        if maxhp < hp then return end

        owner:SetHealth(math.Clamp( hp + self.HealAmount, 0, maxhp ))

    end)

end

function SWEP:Infection(dmg)

    if !(math.random(0.01,1.00) >= self.InfectChance) then return end

    if !dmg:IsValid() then return end

    if !dmg:IsPlayer() then return end

    if !dmg:Alive() then return end

    if dmg:HasWeapon(self:GetClass()) then return end

    local id, step, cnt, rgb

    id = "WerewolfInfectionTimer_"..dmg:Name()

    step = math.floor(230/self.InfectDuration)

    if timer.Exists(id) then return end

    cnt = 0

    dmg:SetRenderMode( RENDERMODE_TRANSALPHA )

    if SERVER then dmg:ChatPrint(""..(self.InfectDuration*5).." seconds.") end

    dmg:EmitSound("eoti_idlegrowlloop", 350, math.random(23,40))

    timer.Create(id, 5, self.InfectDuration, function()

        if !self:IsValid()

        or !dmg:IsValid()

        or !dmg:IsPlayer()

        or !dmg:Alive()

        or dmg:HasWeapon(self:GetClass())

        or !timer.Exists(id)

        then

            dmg:SetColor( Color(255,255,255) )

            dmg:SetRenderMode( RENDERMODE_NORMAL )

            timer.Destroy(id)

            return false

        end

        rgb = 255 - (cnt * step)

        cnt = cnt + 1

        dmg:SetColor( Color(rgb,rgb,rgb) )

        if cnt < self.InfectDuration then return end

        if not SERVER and CLIENT then return end

        dmg:StopSound("eoti_idlegrowlloop")

        dmg:Give(self:GetClass())

        dmg:SetColor( Color(255,255,255) )

        dmg:SetRenderMode( RENDERMODE_NORMAL )

        timer.Destroy(id)

        return true

    end)

end

function SWEP:Think()

    local t

    if game.MaxPlayers() < 2 then t = CurTime()

    else t = SysTime() end

    if self.AnimDelay > t then return true end

    local owner, primary

    owner = self.Owner

    primary = (self:GetNextPrimaryFire() - CurTime())

    if self.PlayerModel == nil then

        self.PlayerModel = ""..self.Owner:GetModel()

        self.PlayerScale = self.Owner:GetModelScale() or 1

        self.WerewolfScale = self.PlayerScale * 1.0

        self.WalkSpeed = owner:GetWalkSpeed()

        self.RunSpeed = owner:GetRunSpeed()

        return true

    elseif owner:KeyDown(IN_USE) then

        self.ToggleVFX = !self.ToggleVFX

        if CLIENT then surface.PlaySound("UI/buttonclick.wav") end

        self.AnimDelay = t + 0.5

        return true

    elseif owner:GetModel() == self.PlayerModel then

        owner:SetRunSpeed(self.RunSpeed)

        owner:SetWalkSpeed(self.WalkSpeed)

        self.AnimDelay = t + 0.45

        return true

    elseif owner:KeyDown(IN_FORWARD) and !owner:KeyDown(IN_DUCK) then

        owner:SetRunSpeed(math.Clamp(self.RunSpeed*self.SpeedModifier, 450, 1000))

        owner:SetWalkSpeed(math.Clamp(self.WalkSpeed*self.SpeedModifier, 375, 1000))

        owner:DoAnimationEvent(ACT_HL2MP_RUN_ZOMBIE_FAST)

        self.AnimDelay = t + 0.4

        return false

    elseif t + primary > t then

        self.AnimDelay = primary + 0.05

        return true

    end

    self.AnimDelay = t + 0.5

end

[Gmod4phun]

Check if the viewmodel actually exists before trying to play animations on it. Also, what is with the spaces everywhere dude?

[GorkemF]

i have a hard time seeing bulked text so its easy for me to separate them like that with spaces :P

ps : is there a gmod wiki page that i can relate to for what you said

[_Fancy_]

IsValid
local vm = self.Owner:GetViewModel()
if IsValid(vm) then
vm:ResetSequence( vm:LookupSequence( "fists_draw" ) )
end