added error and message to source code regarding unfinalized block height
added error and message to source code regarding unfinalized block height

fczuardi/vanillacoin,openvcash/vcash,openvcash/vcash,xCoreDev/vcash,sum01/vcash,xCoreDev/vcash,fczuardi/vanillacoin,sum01/vcash,xCoreDev/vanillacoin,xCoreDev/vanillacoin