Fix build due to unimplemented virtual functions
Fix build due to unimplemented virtual functions

yann300/mix,LianaHus/mix,LianaHus/mix,chriseth/mix,yann300/mix,LefterisJP/mix,LefterisJP/mix,LefterisJP/mix,chriseth/mix,vaporry/mix,tomthebuzz/mix,tomthebuzz/mix,ethereum/mix,ethereum/mix,ethereum/mix,chriseth/mix,LianaHus/mix,vaporry/mix,yann300/mix,vaporry/mix,tomthebuzz/mix