Fix warnings about passing values to type void.

Author: timbotimbo

lib/src/helpers/events.dart

@@ -5,13 +5,13 @@ class UnityEvent<T> {
   final int unityId;
 
   /// The value wrapped by this event
-  final T value;
+  final T? value;
 
   /// Build a Unity Event, that relates a mapId with a given value.
   ///
   /// The `unityId` is the id of the map that triggered the event.
   /// `value` may be `null` in events that don't transport any meaningful data.
-  UnityEvent(this.unityId, this.value);
+  UnityEvent(this.unityId, [this.value]);
 }
 
 class UnitySceneLoadedEvent extends UnityEvent<SceneLoaded?> {
@@ -20,15 +20,15 @@ class UnitySceneLoadedEvent extends UnityEvent<SceneLoaded?> {
 }
 
 class UnityLoadedEvent extends UnityEvent<void> {
-  UnityLoadedEvent(int unityId, void value) : super(unityId, value);
+  UnityLoadedEvent(int unityId) : super(unityId);
 }
 
 class UnityUnLoadedEvent extends UnityEvent<void> {
-  UnityUnLoadedEvent(int unityId, void value) : super(unityId, value);
+  UnityUnLoadedEvent(int unityId) : super(unityId);
 }
 
 class UnityCreatedEvent extends UnityEvent<void> {
-  UnityCreatedEvent(int unityId, void value) : super(unityId, value);
+  UnityCreatedEvent(int unityId) : super(unityId);
 }
 
 class UnityMessageEvent extends UnityEvent<dynamic> {

lib/src/io/device_method.dart

@@ -86,14 +86,14 @@ class MethodChannelUnityWidget extends UnityWidgetPlatform {
         _unityStreamController.add(UnityMessageEvent(unityId, call.arguments));
         break;
       case "events#onUnityUnloaded":
-        _unityStreamController.add(UnityLoadedEvent(unityId, call.arguments));
+        _unityStreamController.add(UnityLoadedEvent(unityId));
         break;
       case "events#onUnitySceneLoaded":
         _unityStreamController.add(UnitySceneLoadedEvent(
             unityId, SceneLoaded.fromMap(call.arguments)));
         break;
       case "events#onUnityCreated":
-        _unityStreamController.add(UnityCreatedEvent(unityId, call.arguments));
+        _unityStreamController.add(UnityCreatedEvent(unityId));
         break;
       default:
         throw UnimplementedError("Unimplemented ${call.method} method");

lib/src/web/web_unity_widget_controller.dart

@@ -107,7 +107,7 @@ class WebUnityWidgetController extends UnityWidgetController {
           unityReady = true;
           unityPause = false;
 
-          _unityStreamController.add(UnityCreatedEvent(0, {}));
+          _unityStreamController.add(UnityCreatedEvent(0));
           return;
         }