title: Collection element of type 'void *' is not an Objective-C object
body: <p>Im trying to add the a gradient view to my background on for an iOS app.</p>
  
  <p>Using the pod <code>UIColor+uiGradients</code> I am adding a GradientLayer to my background under <code>viewDidLoad</code>:</p>
  
  <pre><code>- (void)viewDidLoad {
      [super viewDidLoad];
      UIColor *startColor = [UIColor uig_emeraldWaterStartColor];
      UIColor *endColor = [UIColor uig_emeraldWaterEndColor];
  
      CAGradientLayer *gradient = [CAGradientLayer layer];
      gradient.frame = self.view.bounds;
      gradient.startPoint = CGPointMake(0, 0);
      gradient.endPoint = CGPointMake(self.view.frame.size.width, 0);
      gradient.colors = @[(id)[startColor CGColor], (id)[endColor CGColor], nil];
  
      [self.view.layer insertSublayer:gradient atIndex:0];   
  }
  </code></pre>
  
  <p>The error occurs on line <code>gradients.colors =  @[(id)[startColor CGColor], (id)[endColor CGColor], nil];</code></p>
  
  <p>error :</p>
  
  <blockquote>
    <p>Collection element of type 'void *' is not an Objective-C object. </p>
  </blockquote>
  
  <p>Thanks for any assistance.</p>