fix compile issue
fix compile issue

NicolasDorier/NBitcoin,stratisproject/NStratis,thepunctuatedhorizon/BrickCoinAlpha.0.0.1,dangershony/NStratis,lontivero/NBitcoin,HermanSchoenfeld/NBitcoin,MetacoSA/NBitcoin,MetacoSA/NBitcoin