title: Panel:Center() is not centring the Derma Frame
body: <p>I've created a Derma Frame, and when I call Center() on that frame it doesn't properly center to the screen. </p>
  
  <p>Screenshot:</p>
  
  <p><img src="https://i.stack.imgur.com/GIKQd.jpg" alt="1]"></p>
  
  <p>Here's the code:</p>
  
  <pre><code>local ply = LocalPlayer()
  
  hook.Add("OnPlayerChat", "Link:lnotify:OnPlayerChat", function(ply, text, teamChat, isDead)
      if(ply:IsSuperAdmin()) then
          if (text == "!lnotify") then
              local lnotifyAdminMenu = vgui.Create("DFrame")
              lnotifyAdminMenu:Center()
              lnotifyAdminMenu:SetSize(1000, 720)
              lnotifyAdminMenu:ShowCloseButton(true)
              lnotifyAdminMenu:MakePopup()
          end
      else
          Derma_Message("You're not permitted to use this menu", "Access Denied", "OK")
      end
  end)
  </code></pre>