Removed `willSet`s

Sources/iOS/TabBar.swift

@@ -249,10 +249,8 @@ open class TabBar: Bar {
   
   /// The currently selected tabItem.
   open internal(set) var selectedTabItem: TabItem? {
-    willSet {
-      selectedTabItem?.isSelected = false
-    }
     didSet {
+      oldValue?.isSelected = false
       selectedTabItem?.isSelected = true
     }
   }

Sources/iOS/TransitionController.swift

@@ -57,22 +57,15 @@ open class TransitionController: UIViewController {
    helper method.
    */
   open internal(set) var rootViewController: UIViewController! {
-    willSet {
-      guard newValue != rootViewController else {
-        return
-      }
-      
-      guard let v = rootViewController else {
-        return
-      }
-      
-      removeViewController(viewController: v)
-    }
     didSet {
       guard oldValue != rootViewController else {
         return
       }
       
+      if let v = oldValue {
+        removeViewController(viewController: v)
+      }
+      
       prepare(viewController: rootViewController, in: container)
     }
   }