check for not result instead of result === undefined
check for not result instead of result === undefined

imjerrybao/node-gcm,pablonazareno/node-gcm,mauron85/node-gcm,bastienleonard/node-gcm,SpireTeam/yodel-gcm,SpireTeam/spire-fcm,surespot/node-gcm,kaija/node-gcm