fix: failing assertion in flame library

  'package:flame/src/components/sprite_animation_group_component.dart': Failed assertion: line 143 pos 12: '_animations != null': Animations not set
  dart:core                                                                  _AssertionError._throwNew
  package:flame/src/components/sprite_animation_group_component.dart 143:12  SpriteAnimationGroupComponent.current=
  package:ricochlime/flame/components/monster.dart 372:7                     MonsterAnimation.walking=

lib/flame/components/monster.dart

@@ -353,7 +353,9 @@ class MonsterAnimation extends SpriteAnimationGroupComponent<MonsterState>
           removeOnFinish: {
             MonsterState.dead: true,
           },
-        );
+        ) {
+    animations = getAnimations(monsterImagePath: monsterImagePath);
+  }
 
   static const staticWidth = 20.0;
   static const staticHeight = staticWidth;
@@ -377,7 +379,6 @@ class MonsterAnimation extends SpriteAnimationGroupComponent<MonsterState>
 
   @override
   Future<void> onLoad() async {
-    animations = getAnimations();
     current = MonsterState.idle;
     walking = _walking;
     await super.onLoad();
@@ -408,7 +409,9 @@ class MonsterAnimation extends SpriteAnimationGroupComponent<MonsterState>
     final animations = this.animations;
     if (animations == null) return;
 
-    final monsterImage = gameRef.images.fromCache(monsterImagePath);
+    // Swap the sprite in existing animations
+    final monsterImage =
+        RicochlimeGame.instance.images.fromCache(monsterImagePath);
     for (final animation in animations.values) {
       for (final frame in animation.frames) {
         frame.sprite.image = monsterImage;
@@ -417,8 +420,11 @@ class MonsterAnimation extends SpriteAnimationGroupComponent<MonsterState>
   }
 
   /// The list of animations for the monster.
-  Map<MonsterState, SpriteAnimation> getAnimations() {
-    final monsterImage = gameRef.images.fromCache(monsterImagePath);
+  static Map<MonsterState, SpriteAnimation> getAnimations({
+    required String monsterImagePath,
+  }) {
+    final monsterImage =
+        RicochlimeGame.instance.images.fromCache(monsterImagePath);
     return {
       MonsterState.idle: SpriteAnimation.fromFrameData(
         monsterImage,

test/new_row_test.dart

@@ -10,10 +10,12 @@ void main() {
   group('New row generation', () {
     test(
         'At least ${RicochlimeGame.minMonstersInRow} and '
-        'at most ${Monster.monstersPerRow} monsters are generated', () {
+        'at most ${Monster.monstersPerRow} monsters are generated', () async {
+      TestWidgetsFlutterBinding.ensureInitialized();
       SharedPreferences.setMockInitialValues({});
       Prefs.testingMode = true;
       Prefs.init();
+      await RicochlimeGame.instance.preloadSprites.future;
 
       final random = Random(12);
       expect(RicochlimeGame.minMonstersInRow, lessThan(Monster.monstersPerRow));