title: Container view controller app crash NSInternalInconsistencyException in Swift?
body: <p>I have a <code>UIViewcontroller</code> with a container view inside. In the <code>storyboard</code>, the container view is connected with the <code>UIViewcontroller</code> through an Embed Segue. I do not need to pass data from the <code>ParentView Controller</code> to the Child View Controller. The <code>ChildViewController</code> has a <code>CustomViewController</code> class, but since I don't need to pass any data between the 2 view controllers, the only reference between them is the embed segue in the <code>Storyboard</code>.</p>
  
  <p>Every time I open the parent view controller, the app crashes, with the following error:</p>
  
  <blockquote>
    <p>*** Terminating app due to uncaught exception 'NSInternalIncosistencyException',
        reason: 'NSDictionaryOfVariableBindings failed bacause either one of the values 
        is nil, or there's something wrong with the way the macro is being invoked.
        Cannot assign value nil for key "childView". Keys:(
            childView
        )'</p>
  </blockquote>
  
  <p>Any idea what is causing this error and how to fix this? I'm working with Xcode 8.1 and Swift 3</p>