added error checking
added error checking

quartzjer/ursa,IbpTeam/node-ursa,IbpTeam/node-ursa,IbpTeam/node-ursa,mansona/ursa,darrenmce/ursa,davedoesdev/ursa,mansona/ursa,darrenmce/ursa,darrenmce/ursa,davedoesdev/ursa,quartzjer/ursa,davedoesdev/ursa,mansona/ursa,mansona/ursa,quartzjer/ursa,darrenmce/ursa,IbpTeam/node-ursa