adding file check to zcash binary path validation
adding file check to zcash binary path validation

OpenBazaar/openbazaar-desktop,OpenBazaar/openbazaar-desktop,jjeffryes/openbazaar-desktop,jashot7/openbazaar-desktop,jashot7/openbazaar-desktop,OpenBazaar/openbazaar-desktop,jashot7/openbazaar-desktop,jjeffryes/openbazaar-desktop,jjeffryes/openbazaar-desktop