[Matrix]: return an empty local sparse matrix store if no nz values.
[Matrix]: return an empty local sparse matrix store if no nz values.

flashxio/FlashX,icoming/FlashGraph,icoming/FlashX,icoming/FlashX,icoming/FlashX,icoming/FlashX,flashxio/FlashX,flashxio/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,flashxio/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashGraph,icoming/FlashGraph