Fix for Bitcoin 0.8 blockfiles in datadir with defined chain.
Fix for Bitcoin 0.8 blockfiles in datadir with defined chain.

machado-rev/HTMLCoinExplorer,Cybnate/NuBits-Abe-explorer,cryptapus/bitcoin-abe,muchbeli/bitcoin-abe,machinecoin-project/machinecoin-blockchainexplorer-abe,machado-rev/HTMLCoinExplorer,mmitech/bitcoin-abe,gjhiggins/chaincoin-abe,Rimbit/RimbitExplorer,n00bsys0p/altcoin-abe,jeorgen/bitcoin-abe,Serya05/bitcoin-abe,ultracoindev/ultracoin-abe,Dilmacoin/dilmacoin-abe,muchbeli/bitcoin-abe,gjhiggins/chaincoin-abe,ultracoindev/ultracoin-abe,MatthewLM/PeercoinAbeExplorer,BuckyGreen/latiumexplorer,Cybnate/NuBits-Abe-explorer,Rimbit/RimbitExplorer,jeorgen/bitcoin-abe,machado-rev/HTMLCoinExplorer,gjhiggins/altcoin-abe,mmitech/bitcoin-abe,machinecoin-project/machinecoin-blockchainexplorer-abe,UdjinM6/darkcoin-abe,gjhiggins/abe-bee2,Serya05/bitcoin-abe,muchbeli/bitcoin-abe,cryptapus/bitcoin-abe,MatthewLM/PeercoinAbeExplorer,Dilmacoin/dilmacoin-abe,gjhiggins/altcoin-abe,Rimbit/RimbitExplorer,jeromewu/bitcoin-abe-opennet,MatthewLM/PeercoinAbeExplorer,ultracoindev/ultracoin-abe,muchbeli/bitcoin-abe,UdjinM6/darkcoin-abe,jonnynewbs/bitcoin-abe,Cybnate/NuBits-Abe-explorer,MatthewLM/PeercoinAbeExplorer,jeromewu/bitcoin-abe-opennet,BuckyGreen/latiumexplorer,Cybnate/NuBits-Abe-explorer,BuckyGreen/latiumexplorer,leadcoin-reboot/leadcoin-abe,CraigsCoin/abe-craigscoin,leadcoin-reboot/leadcoin-abe,gjhiggins/abe-bee2,gjhiggins/abe-bee2,ultracoindev/ultracoin-abe,Max-Coin/maxcoin-abe,Max-Coin/maxcoin-abe,Cybnate/NuBits-Abe-explorer,BuckyGreen/latiumexplorer,jonnynewbs/bitcoin-abe,ultracoindev/ultracoin-abe,n00bsys0p/altcoin-abe,machado-rev/HTMLCoinExplorer,CraigsCoin/abe-craigscoin,Rimbit/RimbitExplorer