title: Check if array contains element when the array can be nil
body: <p>I declare an empty array</p>
  
  <pre><code>var myArray: [DWTeaser]?
  </code></pre>
  
  <p>than I want to go through t elements and add them to the array, every element should be added only one time</p>
  
  <pre><code>for t in alltElement {
      if !self.myArray!.contains(t){
          self.myArray?.append(t)
      }
  }
  </code></pre>
  
  <p>The app crashes and I think it's because that the first time myArray is nil. How can I fix that? </p>