HDFS-14598. Findbugs warning caused by HDFS-12487.

Contributed by He Xiaoqiao.

(cherry picked from commit 041e7a7dee)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java

@@ -906,24 +906,17 @@ public class DiskBalancer {
           if(null == block){
             LOG.info("NextBlock call returned null.No valid block to copy. {}",
                     item.toJson());
-            return block;
+            return null;
           }
-
-          if (block != null) {
           // A valid block is a finalized block, we iterate until we get
           // finalized blocks
           if (!this.dataset.isValidBlock(block)) {
             continue;
           }
-
           // We don't look for the best, we just do first fit
           if (isLessThanNeeded(block.getNumBytes(), item)) {
             return block;
           }
-          } else {
-            LOG.info("There are no blocks in the blockPool {}", iter.getBlockPoolId());
-          }
-
         } catch (IOException e) {
           item.incErrorCount();
         }