Fix segfault in miner.cpp
Fix segfault in miner.cpp

bitjson/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind,brishtiteveja/truthcoin-cpp,brishtiteveja/truthcoin-cpp,bitjson/hivemind,brishtiteveja/truthcoin-cpp,brishtiteveja/truthcoin-cpp,bitcoin-hivemind/hivemind,bitcoin-hivemind/hivemind,brishtiteveja/truthcoin-cpp,bitcoin-hivemind/hivemind,brishtiteveja/truthcoin-cpp,bitjson/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind,bitjson/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind,bitcoin-hivemind/hivemind