Make mining on genesis work again.

libethereum/BlockChain.cpp

@@ -1278,6 +1278,7 @@ Block BlockChain::genesisBlock(OverlayDB const& _db)
 	dev::eth::commit(m_genesisState, ret.mutableState().m_state);		// bit horrible. maybe consider a better way of constructing it?
 	ret.mutableState().db().commit();									// have to use this db() since it's the one that has been altered with the above commit.
 	ret.m_previousBlock = BlockInfo(m_genesisBlock);
+	ret.resetCurrent();
 	return ret;
 }