YARN-1243. ResourceManager: Error in handling event type NODE_UPDATE to the scheduler - NPE at SchedulerApp.java:411 (Jason Lowe via jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1526670 13f79535-47bb-0310-9956-ffa450edef68