title: NSDictionary returning nil when unwrapped
body: <p>I'm trying to create detection options for a CIDetector. The NSDictionary i'm creating to hold the detection options keeps giving me the error "unexpected found nil while unwrapping optional value". I've gotten this error but I can't seem to figure it out this time around. </p>
  
  <pre><code>var detectorOptions:NSDictionary = NSDictionary(objectsAndKeys: CIDetectorAccuracyLow,CIDetectorAccuracy)
  </code></pre>