fix: Component.loaded future sometimes failed to complete (#1593)

packages/flame/lib/src/components/component.dart

@@ -501,6 +501,7 @@ class Component {
     final onLoadFuture = onLoad();
     if (onLoadFuture == null) {
       _state = LifecycleState.loaded;
+      _loadCompleter?.complete();
     } else {
       return onLoadFuture.then((_) {
         _state = LifecycleState.loaded;

packages/flame/test/components/component_lifecycle_test.dart

@@ -117,6 +117,17 @@ void main() {
       },
     );
 
+    testWithFlameGame(
+      '.loaded completes even if accessed before the component added to game',
+      (game) async {
+        final component = Component();
+        final loadedFuture = component.loaded;
+        game.add(component);
+        await game.ready();
+        expectLater(loadedFuture, completes);
+      },
+    );
+
     // Obsolete scenario, when we used to have a separate "prepare" stage
     flameGame.test('parent prepares the component', (game) async {
       final parent = _MyComponent('parent');