fix issue #258 : setminingaccount with empty address throw 'std::out_of_range'
fix issue #258 : setminingaccount with empty address throw 'std::out_of_range'

the-metaverse/metaverse,mvs-org/metaverse,the-metaverse/metaverse,mvs-org/metaverse,mvs-org/metaverse,mvs-org/metaverse,mvs-live/metaverse,mvs-live/metaverse,mvs-org/metaverse,mvs-org/metaverse,the-metaverse/metaverse