fix block parsing edge case (credit/debit for asset that doesn't exist or is invalid)
fix block parsing edge case (credit/debit for asset that doesn't exist or is invalid)

paytokens-beta/payblockd,ClearingHouse/clearblockd,Reddcraft/reddblockd,Tetchain/tetblockd,Bluejudy/blueblockd,Tetchain/tetblockd,Reddcraft/reddblockd,CounterpartyXCP/counterblock,ClearingHouse/clearblockd,Paytokens/payblockd,CounterpartyXCP/counterblock,Czarparty/czarblockd,Metronote/metroblockd-alpha,Peertokens/peerblockd,Bluejudy/blueblockd,Litetokens/liteblockd,metronotes-beta/metroblockd,patricklodder/dogeblockd