message: Fix, set mBackend to resolved backend in FilamentApp.cpp
diff: @@ -522,8 +522,6 @@ FilamentApp::Window::Window(FilamentApp* filamentApp,
  windowFlags |= SDL_WINDOW_HIDDEN;
  }
  - mBackend = config.backend;
  -
  // Even if we're in headless mode, we still need to create a window, otherwise SDL will not poll
  // events.
  mWindow = SDL_CreateWindow(title.c_str(), x, y, (int) w, (int) h, windowFlags);
  @@ -540,7 +538,7 @@ FilamentApp::Window::Window(FilamentApp* filamentApp,
  mFilamentApp->mEngine = Engine::create(config.backend);
  // get the resolved backend
  - config.backend = mFilamentApp->mEngine->getBackend();
  + mBackend = config.backend = mFilamentApp->mEngine->getBackend();
  void* nativeWindow = ::getNativeWindow(mWindow);
  void* nativeSwapChain = nativeWindow;
  