when destroying a SceneAsset, if the object is an instance, call destroyInstance on the owner of instance rather than deleting the object directly

thermion_dart/native/src/c_api/TSceneAsset.cpp

@@ -112,8 +112,12 @@ extern "C"
     
     EMSCRIPTEN_KEEPALIVE void SceneAsset_destroy(TSceneAsset *tSceneAsset) { 
         auto *asset = reinterpret_cast<SceneAsset*>(tSceneAsset);
+        if(asset->isInstance()) {
+            asset->getInstanceOwner()->destroyInstance(asset);
+        } else {
             delete asset;
         }
+    }
 
     EMSCRIPTEN_KEEPALIVE void SceneAsset_addToScene(TSceneAsset *tSceneAsset, TScene *tScene) {
         auto *asset = reinterpret_cast<SceneAsset*>(tSceneAsset);