submodule is broken

[jeng1220]

Could someone fix submodule please ?
I got following error message:

fatal: reference is not a tree: 93696c4bce447b71c4bd0b25d1e26f1247341c04
fatal: reference is not a tree: 93696c4bce447b71c4bd0b25d1e26f1247341c04
Unable to checkout '93696c4bce447b71c4bd0b25d1e26f1247341c04' in submodule path 'posts/american-options/external/cub'
Unable to checkout '93696c4bce447b71c4bd0b25d1e26f1247341c04' in submodule path 'posts/parallel_reduction_with_shfl/cub'