[SDL2] PNG - czasami nie wczytuje obrazów

cout << "format: " << img->format->format << "\n";
cout << SDL_GetPixelFormatName( img->format->format );
// converting invalid format to ABGR8888 ( to use in openGL )
SDL_PixelFormat * target = SDL_AllocFormat( SDL_PIXELFORMAT_ABGR8888 );
img = SDL_ConvertSurface( img, target, 0 );