Calculating proper top margin is more succint

Author: Michele Volpato

Examples/NavigationTransitionsExample/Transition/Transition/InteractiveZoomTransitionController.swift

@@ -68,16 +68,12 @@ extension InteractiveZoomTransitionController : SharedElementProvider {
         let targetFrame: CGRect
 
         // Get top margin, depending on possible safe area
-        var yMargin: CGFloat
+        var yMargin = CollectionViewController.margin
 
         if #available(iOS 11.0, *) {
-            yMargin = toViewController.collectionView.safeAreaInsets.top
-        } else {
-            yMargin = 0.0
+            yMargin += toViewController.collectionView.safeAreaInsets.top
         }
 
-        yMargin += CollectionViewController.margin
-        
         if isPresenting {
             initialFrame = fromViewController.targetFrame
             targetFrame = CGRect(origin: CGPoint(x: CollectionViewController.margin, y: yMargin), size: header.image.frame.size)