[Graph]: fix a bug in converting weighted graphs.
[Graph]: fix a bug in converting weighted graphs.

icoming/FlashGraph,icoming/FlashX,zheng-da/FlashX,flashxio/FlashX,flashxio/FlashX,zheng-da/FlashX,flashxio/FlashX,icoming/FlashX,zheng-da/FlashX,zheng-da/FlashX,flashxio/FlashX,icoming/FlashX,zheng-da/FlashX,icoming/FlashGraph,icoming/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashX,icoming/FlashGraph,icoming/FlashGraph,flashxio/FlashX