fix: CameraComponent no longer throws Concurrent modification on stop

.github/.cspell/gamedev_dictionary.txt

@@ -46,6 +46,7 @@ raytracing # rendering techniques that calculates light rays as straight lines
 rects # plural of rect
 respawned # past tense of respawn
 respawn # when the player character dies and is brought back after some time and penalties
+retarget # to direct (something) toward a different target
 RGBA # red green blue alpha
 RGBO # red green blue opacity
 rrect # rounded rect

packages/flame/lib/src/camera/camera_component.dart

@@ -323,7 +323,7 @@ class CameraComponent extends Component {
 
  /// Removes all movement effects or behaviors from the viewfinder.
  void stop() {
- viewfinder.children.forEach((child) {
+ viewfinder.children.toList().forEach((child) {
  if (child is FollowBehavior || child is MoveEffect) {
  child.removeFromParent();
  }

packages/flame/test/camera/camera_component_test.dart

@@ -60,6 +60,20 @@ void main() {
  }
  });
 
+ testWithFlameGame('camera should be able to retarget follow', (game) async {
+ // Creating new camera as the one included with game is not mounted and
+ // will therefore not be queued.
+ final camera = CameraComponent(world: game.world)..addToParent(game);
+ final player = PositionComponent()..addToParent(game.world);
+ final player2 = PositionComponent()..addToParent(game.world);
+ camera.follow(player);
+ camera.follow(player2);
+ await game.ready();
+
+ expect(camera.viewfinder.children.length, 1);
+ expect(camera.viewfinder.children.first, isA<FollowBehavior>());
+ });
+
  testWithFlameGame('follow with snap', (game) async {
  final world = World()..addToParent(game);
  final player = PositionComponent()