How do I fix attempt to index nil with 'className'?

Hello,

I have a serverscript that doesn't work, and I have no idea why..

I'm trying to revamp an old Minigames game, but I'm not the best at scripting, so here is the code:

minigames = {}

local m = game.ServerStorage.Choices:GetChildren()
for i=1,#m do
    table.insert(minigames, m[i])
    end

things = script.Parent:GetChildren()
for i=1,#things do
    if things[i].className == "TextButton" then
            things[i].Text = minigames[i].Name
    else
        table.remove(things, i)
    end
    if things[i].className == "Script" then
        table.remove(things, i)
    if things[i].className == "UIGridLayout" then
            table.remove(things, i)
            if things[i].className == "BoolValue" then
                table.remove(things, i)
    else
    things[i].MouseButton1Click:Connect(function(clicked)
script.Parent.Name = minigames[i].Name
        print(minigames)
        if  script.Parent.Debounce.Value == false then
            script.Parent.Debounce.Value = true
            game.Workspace.ChosenMinigame.Value = minigames[i].Name
            m = Instance.new("Message")
            m.Parent = game.Workspace
            m.Text = "Someone has chosen " .. script.Parent.Name .. " as the next minigame!"
            wait(3)
            m:remove()
        end
    end)
    end
    end
    end
end

Players.Zweiio.PlayerGui.thing.Frame.Padding.Setup:10: attempt to index nil with 'className'