HBASE-23244 NPEs running Canary (apache#784)

Addendum to fix findbugs complaint.

(cherry picked from commit 180fa3e)

Change-Id: I0c451cc915dfc42be07bd2f7bb9d52bb7e1d99b4

Author: saintstack

hbase-server/src/main/java/org/apache/hadoop/hbase/tool/CanaryTool.java

@@ -492,7 +492,7 @@ public Void read() {
           sink.publishReadTiming(serverName, region, column, stopWatch.getTime());
         } catch (Exception e) {
           sink.publishReadFailure(serverName, region, column, e);
-          sink.updateReadFailures(region == null? "NULL": region.getRegionNameAsString(),
+          sink.updateReadFailures(region.getRegionNameAsString(),
               serverName == null? "NULL": serverName.getHostname());
         } finally {
           if (rs != null) {