fix: fixed error activating bottom letter while bonus word animation

lib/game/components/bonus_word.dart

@@ -36,23 +36,31 @@ class BonusWord extends Component with BlocComponent<GameBloc, GameState> {
 
       for (var i = 0; i < letters.length; i++) {
         final letter = letters[i];
-        letter.add(
+        letter
+          ..isEnabled = false
+          ..add(
             SequenceEffect(
               [
                 ColorEffect(
-                i.isOdd ? BonusLetter._activeColor : BonusLetter._disableColor,
+                  i.isOdd
+                      ? BonusLetter._activeColor
+                      : BonusLetter._disableColor,
                   const Offset(0, 1),
                   EffectController(duration: 0.25),
                 ),
                 ColorEffect(
-                i.isOdd ? BonusLetter._disableColor : BonusLetter._activeColor,
+                  i.isOdd
+                      ? BonusLetter._disableColor
+                      : BonusLetter._activeColor,
                   const Offset(0, 1),
                   EffectController(duration: 0.25),
                 ),
               ],
               repeatCount: 4,
             )..onFinishCallback = () {
-              letter.add(
+                letter
+                  ..isEnabled = true
+                  ..add(
                     ColorEffect(
                       BonusLetter._disableColor,
                       const Offset(0, 1),
@@ -107,6 +115,10 @@ class BonusLetter extends BodyComponent<PinballGame>
   final String _letter;
   final int _index;
 
+  /// Indicates if [BonusLetter] could be activated on contact with [Ball].
+  /// Deactivated during animation of [GameBonus.word].
+  bool isEnabled = true;
+
   @override
   Future<void> onLoad() async {
     await super.onLoad();
@@ -172,6 +184,8 @@ class BonusLetterBallContactCallback
     extends ContactCallback<Ball, BonusLetter> {
   @override
   void begin(Ball ball, BonusLetter bonusLetter, Contact contact) {
+    if (bonusLetter.isEnabled) {
       bonusLetter.activate();
     }
   }
+}