title: self.delegate is nil and does not get called
body: <p>I've been struggling with a problem lately, and believe me I wouldn't post here if the solution was online somewhere.
  Here is my problem :</p>
  
  <p>I have a parentVC with 3 childVC linked to it. I have delegates for the 3 of them to report to the parentVC some actions, and it's working for 2 of them and not the 3rd one even if I declared the same thing for the 3 of use.</p>
  
  <p>Here is my code:
  In parentVC.m</p>
  
  <pre><code>// Initializing the clientsListViewController
  self.clientsListViewController = [[UIStoryboard storyboardWithName:@"AGZClientsList" bundle:nil] instantiateInitialViewController];
  [self addChildViewController:self.clientsListViewController];
  [self.clientsListViewController didMoveToParentViewController:self];
  self.clientsListViewController.delegate = self;
  </code></pre>
  
  <p>In my childVC.h</p>
  
  <pre><code>@protocol AGZClientsListViewControllerDelegate &lt;NSObject&gt;
  
  - (void)didClickLeftBarButtonInClientsView:(UIButton*)button;
  
  @end
  
  @interface AGZClientsListViewController : AGZBaseViewController
  
  @property (nonatomic, weak) id &lt;AGZClientsListViewControllerDelegate&gt; delegate;
  
  @end
  </code></pre>
  
  <p>In my childVC.m</p>
  
  <pre><code>- (void)didClickLeftBarButton:(UIButton*)button
  {
      if ([self.delegate respondsToSelector:@selector(didClickLeftBarButtonInClientsView:)])
          [self.delegate didClickLeftBarButtonInClientsView:button];
  }
  </code></pre>
  
  <p>Please help me!</p>