How to get the player from :MouseButton1Click()?

So, I'm making a script and I made a function that is called by :MouseButton1Click() so in the function I made the parameters "plr" and in the function I made this line "if plr.Parent.Parent.PlayerHasBase.Value == false then" and it doesn't work, because the output says plr = nil so then I need help, how do I get the player from a click? Because my way doesn't work.... :c Full script:

function SpawnBase(plr)
    if plr.Parent.Parent.PlayerHasBase.Value == false then
        local Base = game.ServerStorage.Base:Clone()
        Base.Parent = plr.Character
        Base:MoveTo(game.Workspace.Spawn1.Position)
    end
end

script.Parent.MouseButton1Click:connect(SpawnBase)