db_init.cpp:  Fix compiler warning
db_init.cpp:  Fix compiler warning

abitmore/bitshares-2,oxarbitrage/bitshares-core,bigoc/openchain,bitshares/bitshares-2,peertracksinc/muse,bitshares/bitshares-2,abitmore/bitshares-2,bitsuperlab/cpp-play2,cryptonomex/graphene,bigoc/openchain,pmconrad/graphene,bitshares/bitshares-2,cryptonomex/graphene,oxarbitrage/bitshares-core,peertracksinc/muse,cryptonomex/graphene,bigoc/openchain,bigoc/openchain,bitsuperlab/cpp-play2,peertracksinc/muse,peertracksinc/muse,abitmore/bitshares-2,oxarbitrage/bitshares-core,pmconrad/graphene,oxarbitrage/bitshares-core,pmconrad/graphene,abitmore/bitshares-2,bitsuperlab/cpp-play2,bitshares/bitshares-2,pmconrad/graphene