title: I cannot solve this assertion error that occurs in my project
body: <p>I made this cocos2d game and as I was developing it, this assertion error came across randomly in the game. I have spent several weeks trying to solve this, but I have not succeeded yet. The error is </p>
  
  <pre><code>Assertion failure in -[HelloWorldLayer addChild:z:tag:],  *** Terminating app due to uncaught exception of class 'nil'
  </code></pre>
  
  <p>Because I have several addChilds, I cannot find which one it is, and to make matters worse, this assertion error occurs very randomly during the run-through at different times. Also, in xcode, when the assertion error happens, it shows me some binary, so I do not know where this error occurs in my actual code. I have also tried using NSZombies, but for some reason it does not work, and it gives me an NSZombie exception. I will happily give my project to anyone who wishes to help me solve this, as it it hard to understand with just me describing it on here.</p>