Why I have this error Character is not a valid member of Model,this script supposed to work?

Character is not a valid member of Model ^output gives me this error and I don't know what to do

Script

local function equipPet(player,pet)
    local character = player.Character--the problem is here
    if pet ~= nil and character ~= nil then

        if character:FindFirstChild(player.Name.."'s pet") then character[player.Name.."'s pet"]:Destroy() end

        if character.HumanoidRootPart:FindFirstChild("attachmentCharacter")then 
            character.HumanoidRootPart:FindFirstChild("attachmentCharacter"):Destroy() 
        end

        pet.Name = player.Name.."'s pet"        

        pet:SetPrimaryPartCFrame(character.HumanoidRootPart.CFrame)

        local modelSize = pet.PrimaryPart.CFrame

        local attachmentCharacter = Instance.new("Attachment")
        attachmentCharacter.Visible = false
        attachmentCharacter.Name = "attachmentCharacter"
        attachmentCharacter.Parent = character.HumanoiRootPart
        attachmentCharacter.Position = Vector3.new(1,1,0) + modelSize

        local attachmentPet = Instance.new("Attachment")
        attachmentPet.Visible = false
        attachmentPet.Parent = pet.PrimaryPart

        local alignPosition = Instance.new("AlignPosition")
        alignPosition.MaxForce = 25000
        alignPosition.Attachment0 = attachmentPet
        alignPosition.Attachment1 = attachmentCharacter
        alignPosition.Responsiveness = 25
        alignPosition.Parent = pet.PrimaryPart

        local alignOrientation = Instance.new("AlignOrientation")
        alignOrientation.MaxTorque = 25000
        alignOrientation.Attachment0 = attachmentPet
        alignOrientation.Attachment1 = attachmentCharacter
        alignOrientation.Responsiveness = 25
        alignOrientation.Parent = pet

        pet.Parent = character


    end



end


game.Players.PlayerAdded:Connect(function(player)
---------------Cash system------------------------
    local leaderstats = Instance.new("Folder")
    leaderstats.Name = "leaderstats"
    leaderstats.Parent = player

    local cash = Instance.new("IntValue")
    cash.Name = "Cash"
    cash.Parent = leaderstats
--------------------------------------------------  

    local inventory = Instance.new("Folder")
    inventory.Name = "PetInventory"
    inventory.Parent = player

    local equippedPet = Instance.new("StringValue")
    equippedPet.Name = "EquippedPet"
    equippedPet.Parent = player 

    player.CharacterAdded:Connect(function(char)
        if game.ReplicatedStorage:WaitForChild("Pets"):FindFirstChild(equippedPet.Value)then
            equipPet(player,game.ReplicatedStorage:WaitForChild("Pets"):FindFirstChild(equippedPet.Value):Clone())
        end 
    end)

    equippedPet.Changed:Connect(function()
        if equippedPet.Value ~= nil then
            if game.ReplicatedStorage:WaitForChild("Pets"):FindFirstChild(equippedPet.Value)then
            equipPet(player,game.ReplicatedStorage:WaitForChild("Pets"):FindFirstChild(equippedPet.Value):Clone())
            end
        end
    end)
    wait(5)
    equipPet(game.ReplicatedStorage.Pets.Storm)--script that equips a pet called "storm"

end)