Turn into character script does not work, can anyone explain me what is wrong with the script?

So, I'm working on a game where you can turn into a prop as soon as you click a part in workspace. The problem is that it does work until you become the prop, after that you can't click the parts again and you get errors if you click somewhere (even if you click the sky). Can anyone help me with this?

Localscript:

local events = game.ReplicatedStorage.Events
local colorevent = events.ChangeColor
local Player = game.Players.LocalPlayer
local Mouse = Player:GetMouse()
local gui = Player.PlayerGui
local mouseM = gui.HUD.MouseMessage
local props = game.ReplicatedStorage.Props

colorevent.OnClientEvent:connect(function(Color)

end)

Mouse.Move:connect(function()
    local X, Y = Mouse.X, Mouse.Y
    if Mouse.Target ~= nil then
    local a = Mouse.Target.Position
    if Mouse.Target.Parent:FindFirstChild("IsProp") and
        X > gui.HUD.AbsolutePosition.x and
        X > gui.HUD.AbsolutePosition.x and
        X < gui.HUD.AbsolutePosition.x+gui.HUD.AbsoluteSize.x and
        Y < gui.HUD.AbsolutePosition.y+gui.HUD.AbsoluteSize.y 
        then
    if Player:DistanceFromCharacter(a) < 18 then
        mouseM.Visible = true;
        mouseM.Position = UDim2.new(0,X+1,0,Y+1);
        mouseM.Text = "Turn into a "..Mouse.Target.Parent.IsProp.Propname.Value;
        Mouse.Button1Down:connect(function()
            local b = Mouse.Target.Parent.IsProp.Propname.Value
            events.SpawnCharacters:FireServer("unfinished",b)
        end)
    else
        mouseM.Visible = false;
        mouseM.Text = ""
    end
    else
        mouseM.Visible = false;
        mouseM.Text = ""
    end
    end
end)

This is the error:

16:29:20.864 - Players.Player1.PlayerScripts.Framework:28: attempt to index field 'Target' (a nil value)
16:29:20.865 - Stack Begin
16:29:20.866 - Script 'Players.Player1.PlayerScripts.Framework', Line 28
16:29:20.867 - Stack End