Update error message for zero hash change.
Update error message for zero hash change.

wallclockbuilder/btcd,Roasbeef/btcd,btcsuitereleases/btcd,aakselrod/btcd,FactomProject/btcd,btcsuite/btcd,tb00/btcd,jrick/btcd,FactomProject/btcd,jongillham/btcd,dajohi/btcd,toddfries/btcd,jcmincke/dcrd,jcmincke/dcrd,Dirbaio/btcd,tb00/btcd,decred/dcrd,cjepson/btcd,jimmysong/btcd,mathiasrw/btcd,jimmysong/btcd,qchain/btcd,davecgh/btcd,1d4Nf6/btcd,stevenroose/btcd,aakselrod/btcd,Cleawing/btcd,danoctavian/btcd,Dirbaio/btcd,glv2/ppcd,btcsuite/btcd,sysbot/btcd,Roasbeef/btcd,glv2/ppcd,BitGo/prova,mathiasrw/btcd,ppcsuite/ppcd-old,jrick/dcrd,cqswxj2013/btcd,btcsuitereleases/btcd,CryptocurrencyCabal/htcd,pkothbauer/btcd,adiabat/btcd,dan-da/btcd,decred/dcrd,Dirbaio/btcd,ppcsuite/ppcd,1d4Nf6/btcd,ltcsuite/ltcd,runeaune/btcd,jrick/btcd,hectorj/btcd,DanielKrawisz/btcd,Stash-Crypto/btcd,jongillham/btcd,dan-da/btcd,ltcsuite/ltcd,qchain/btcd,Cleawing/btcd,ppcsuite/ppcd-old,runeaune/btcd,dajohi/btcd,danoctavian/btcd,cjepson/btcd,wallclockbuilder/btcd,BitGo/prova,jrick/btcd,cqswxj2013/btcd,soapboxsys/ombfullnode,hectorj/btcd,sysbot/btcd,ppcsuite/ppcd,CryptocurrencyCabal/htcd,adiabat/btcd,stevenroose/btcd,jrick/dcrd,pkothbauer/btcd,dajohi/btcd,DanielKrawisz/btcd,toddfries/btcd,jcmincke/dcrd,davecgh/btcd,soapboxsys/ombfullnode,Stash-Crypto/btcd