HBASE-27859 HMaster.getCompactionState can happen NPE when region state is closed (#5232)

Signed-off-by: Duo Zhang <zhangduo@apache.org>
Signed-off-by: Wellington Chevreuil <wchevreuil@apache.org>

Author: guluo2016

hbase-server/src/main/java/org/apache/hadoop/hbase/master/HMaster.java

@@ -4208,6 +4208,11 @@ public CompactionState getCompactionState(final TableName tableName) {
           continue;
         }
         RegionMetrics regionMetrics = sl.getRegionMetrics().get(regionInfo.getRegionName());
+        if (regionMetrics == null) {
+          LOG.warn("Can not get compaction details for the region: {} , it may be not online.",
+            regionInfo.getRegionNameAsString());
+          continue;
+        }
         if (regionMetrics.getCompactionState() == CompactionState.MAJOR) {
           if (compactionState == CompactionState.MINOR) {
             compactionState = CompactionState.MAJOR_AND_MINOR;