title: Unity MissingReferenceException when loading same scene for second time
body: <p>I'm trying to create Arkanoid 3d game using Unity with C#. I've created simple Menu (Scene 0), where I can start my game, my main scene where actual game takes place(Scene 1) and Scoreboard (Scene 2), which is shown after losing all 3 balls Player has at start. After pressing any key i go back to Menu and can start game again. And this is where problem begins.</p>
  
  <p>During second game after loosing 1st ball, my game goes crazy. I get loads of "MissingReferenceException"s  like one below (but some linked to other objects (like GUIText's etc):</p>
  
  <pre><code>MissingReferenceException: The object of type 'Player' has been destroyed but
  you are still trying to access it.
  Your script should either check if it is null or you should not destroy the object.
  Player.BallLost () (at Assets/Player/Player.cs:164)
  GameEventManager.TriggerBallLost () (at Assets/Menagers/GameEventManager.cs:30)
  Ball.Update () (at Assets/Ball/Ball.cs:47)
  </code></pre>
  
  <p>I noticed loads of MissingReferenceExceptions that are casued by not assigning variables. But this feels kinda diffrent for me since it all works perfectly during "1st play". What can cause this problem? I cheked in inspector after launching game for the second game and all variables are assigned to objects.</p>
  
  <p>I'm not sure if shoudl insert game code since it has grown rather big and is split into >10 scripts. </p>