title: Parse Framework throws NSInvalidArgumentException
body: <p>I am trying to include the parse framework into an existing iOS App. I followed the Parse iOS Quick Start Tutorial by adding</p>
  
  <pre><code>- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
  {
    ...
    [Parse setApplicationId:@"..." clientKey:@"..."];
  }
  </code></pre>
  
  <p>and than calling</p>
  
  <pre><code>- (void)viewDidLoad
  {
    ...
    PFObject *testObject = [PFObject objectWithClassName:@"TestObject"];
    testObject[@"foo"] = @"bar";
    [testObject saveInBackground];
  }
  </code></pre>
  
  <p>of course including the import statements.
  Anyway, the problem is that <code>[testObject saveInBackground];</code> throws the following exception:</p>
  
  <blockquote>
    <p>2015-05-29 16:39:25.845 shell[306:80175] <strong>* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*</strong> setObjectForKey: key cannot be nil'</p>
  </blockquote>
  
  <p>I was already searching a lot for a solution for this but cannot find any hint. Also I tried integrating Parse in a new empty project and it worked fine.</p>
  
  <p>Has anyone an idea what could be the problem here?</p>