title: swift handling NSData initialisation fails
body: <p>I have the following line:</p>
  
  <pre><code>let jsonResults = NSData(contentsOfURL: Fetcher.URLforLicenseInfo())
  </code></pre>
  
  <p>This compiles and executes fine but if the initialisation of NSData fails I get an exception later in the code. I have tried to add another line:</p>
  
  <pre><code>if jsonResults != nil { ///blah, blah...
  </code></pre>
  
  <p>but then the compiler complains <code>"Cannot invoke '!=' with an argument list type '(NSData, NilLiteralConvertible)"</code></p>
  
  <p>Shouldn't the compiler recognise NSData initialiser return type as an optional?</p>