fix 'final_fee' referenced before assignment when unspent empty
fix 'final_fee' referenced before assignment when unspent empty

Dogeparty/dogepartyd,stefcrypto/counterparty-lib,monaparty/counterparty-lib,Paytokens/paytokensd,Litetokens/litetokensd,Peertokens/peertokensd,coinwarp/dogeparty-lib,Bluejudy/bluejudyd,tokenly/counterparty-lib,ClearingHouse/clearinghoused,Ziftr/counterpartyd,Reddcraft/reddcraftd,monaparty/counterparty-lib,F483/counterparty-lib,paytokens-beta/paytokensd,ClearingHouse/clearinghoused,CounterpartyXCP/counterparty-lib,Tetchain/tetchaind,Czarparty/czarpartyd,Tetchain/tetchaind,Bluejudy/bluejudyd,Reddcraft/reddcraftd,Ziftr/counterpartyd,metronotes-beta/metronotesd,CounterpartyXCP/counterparty-lib,gotcha/testcounter,Metronote/metronotesd-alpha,patricklodder/dogepartyd,F483/counterparty-lib,jarymoth/counterpartyd,Dogeparty/dogepartyd