HDFS-15459. TestBlockTokenWithDFSStriped fails intermittently. Contributed by Ahmed Hussein.

(cherry picked from commit e7aa4da0a26988fcf5880311067e62a15e05fc1e)

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockTokenWithDFSStriped.java

@@ -136,7 +136,7 @@ public class TestBlockTokenWithDFSStriped extends TestBlockTokenWithDFS {
     LocatedBlock[] internalBlocks = StripedBlockUtil.parseStripedBlockGroup
         (lsb, cellSize, dataBlocks, parityBlocks);
     for (LocatedBlock internalBlock : internalBlocks) {
-      if(super.isBlockTokenExpired(internalBlock)){
+      if(internalBlock != null && super.isBlockTokenExpired(internalBlock)) {
         return true;
       }
     }