The given key was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at ZombieBlocks.HeadlessServer.UpdateBlockSettled(GameTime gameTime, DroppedBlock block, Boolean wasSettled)
   at ZombieBlocks.HeadlessServer.UpdateBlocksNew(GameTime gameTime)
   at ZombieBlocks.HeadlessServer.UpdateGameLogic(GameTime gameTime)
   at ZombieBlocks.HeadlessServer.Update(GameTime gameTime)
   at Microsoft.Xna.Framework.Game.Update(GameTime gameTime)
   at Microsoft.Xna.Framework.Game.Tick()
   at Microsoft.Xna.Framework.Game.HostIdle(Object sender, EventArgs e)
   at Microsoft.Xna.Framework.GameHost.OnIdle()
   at Microsoft.Xna.Framework.WindowsGameHost.RunOneFrame()
   at Microsoft.Xna.Framework.WindowsGameHost.ApplicationIdle(Object sender, EventArgs e)
   at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FDoIdle(Int32 grfidlef)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at Microsoft.Xna.Framework.WindowsGameHost.Run()
   at Microsoft.Xna.Framework.Game.RunGame(Boolean useBlockingRun)
   at ZombieBlocks.Program.Main(String[] args)