YARN-7947. Capacity Scheduler intra-queue preemption can NPE for non-schedulable apps. Contributed by Eric Payne.

(cherry picked from commit bdd2a184d78379d99c802a43ebec7d2cef0bbaf7)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/FifoIntraQueuePreemptionPlugin.java

@@ -412,7 +412,7 @@ public class FifoIntraQueuePreemptionPlugin
         TempUserPerPartition tmpUser = new TempUserPerPartition(
             tq.leafQueue.getUser(userName), tq.queueName,
             Resources.clone(userResourceUsage.getUsed(partition)),
-            Resources.clone(userSpecificAmUsed),
+            Resources.clone(amUsed),
             Resources.clone(userResourceUsage.getReserved(partition)),
             Resources.none());