[Matrix]: fix a bug in unit test of in-mem vector_vector.
[Matrix]: fix a bug in unit test of in-mem vector_vector.

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