return RPC error for invalid block heights
return RPC error for invalid block heights

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