Improve exception safety with smart pointers

Would you like to [wrap any pointer data members](https://github.com/cyrillefavreau/Sol-R/blob/983cc6953c23dc2b2e129379349b654eded40048/apps/scenes/animation/MetaballsScene.cpp#L54 "Update candidate: MetaballsScene class") with the class template “[std::unique_ptr](https://en.wikipedia.org/wiki/Smart_pointer#unique_ptr "Description for the usage of smart pointers")”?