fix(ios): prevent icon animation in TabGroup when closing modal windows

iphone/Classes/TiUITabProxy.h

@@ -28,6 +28,7 @@
   BOOL hasFocus;
   BOOL iconOriginal;
   BOOL activeIconOriginal;
+  UITraitCollection *lastTabBarTraitCollection;
 
   id<TiOrientationController> parentOrientationController;
 

iphone/Classes/TiUITabProxy.m

@@ -44,6 +44,7 @@ - (void)_destroy
   RELEASE_TO_NIL(rootWindow);
   RELEASE_TO_NIL(controller);
   RELEASE_TO_NIL(current);
+  RELEASE_TO_NIL(lastTabBarTraitCollection);
   RELEASE_TO_NIL(fullWidthBackGestureRecognizer);
 
   [super _destroy];
@@ -79,7 +80,36 @@ - (void)_configure
 
 - (void)didChangeTraitCollection:(NSNotification *)info
 {
-  [self updateTabBarItem];
+  __weak TiUITabProxy *weakSelf = self;
+  TiThreadPerformOnMainThread(
+      ^{
+        TiUITabProxy *strongSelf = weakSelf;
+        if (strongSelf == nil) {
+          return;
+        }
+
+        // If a modal is being dismissed, trait collection changes from UIKit
+        // are spurious — the tab bar item doesn't need rebuilding.
+        if (strongSelf->controller.presentedViewController != nil) {
+          return;
+        }
+
+        UITraitCollection *currentTraitCollection = strongSelf->controller.traitCollection;
+        if (currentTraitCollection == nil) {
+          currentTraitCollection = strongSelf->rootWindow.hostingController.traitCollection;
+        }
+        if (currentTraitCollection == nil) {
+          return;
+        }
+        if ((strongSelf->lastTabBarTraitCollection != nil)
+            && ![currentTraitCollection hasDifferentColorAppearanceComparedToTraitCollection:strongSelf->lastTabBarTraitCollection]
+            && (currentTraitCollection.horizontalSizeClass == strongSelf->lastTabBarTraitCollection.horizontalSizeClass)
+            && (currentTraitCollection.verticalSizeClass == strongSelf->lastTabBarTraitCollection.verticalSizeClass)) {
+          return;
+        }
+        [strongSelf updateTabBarItem];
+      },
+      NO); // NO = non-blocking, since this is a notification handler
 }
 
 - (NSString *)apiName
@@ -558,6 +588,10 @@ - (void)updateTabBarItem
   ENSURE_UI_THREAD_0_ARGS;
 
   UIViewController *rootController = [rootWindow hostingController];
+  UITraitCollection *currentTraitCollection = controller.traitCollection;
+  if (currentTraitCollection == nil) {
+    currentTraitCollection = rootController.traitCollection;
+  }
   id badgeValue = [TiUtils stringValue:[self valueForKey:@"badge"]];
   id badgeColor = [self valueForKey:@"badgeColor"];
   id iconInsets = [self valueForKey:@"iconInsets"];
@@ -581,6 +615,8 @@ - (void)updateTabBarItem
     [newItem release];
 
     systemTab = YES;
+    [lastTabBarTraitCollection release];
+    lastTabBarTraitCollection = [currentTraitCollection retain];
     return;
   }
 
@@ -707,6 +743,9 @@ - (void)updateTabBarItem
   [tabBarItem setBadgeValue:badgeValue];
 
   systemTab = NO;
+
+  [lastTabBarTraitCollection release];
+  lastTabBarTraitCollection = [currentTraitCollection retain];
 }
 
 - (UIEdgeInsets)calculateIconInsets:(id)value