From 574a6a9d653a1ad078d8d0ba54cb0c3ac2ceac1d Mon Sep 17 00:00:00 2001
From: Christine Poerschke <cpoerschke@apache.org>
Date: Wed, 11 May 2016 13:42:46 +0100
Subject: [PATCH] SOLR-9093: Fix NullPointerException in
 TopGroupsShardResponseProcessor.

---
 solr/CHANGES.txt                                                | 2 ++
 .../responseprocessor/TopGroupsShardResponseProcessor.java      | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index ec413b1677a..152bc9158d3 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -170,6 +170,8 @@ Bug Fixes
 * SOLR-9058: Makes HashJoinStream and OuterHashJoinStream support different field names in the 
   incoming streams, eg. fieldA=fieldB. (Dennis Gove, Stephan Osthold)
 
+* SOLR-9093: Fix NullPointerException in TopGroupsShardResponseProcessor. (Christine Poerschke)
+
 Optimizations
 ----------------------
 * SOLR-8722: Don't force a full ZkStateReader refresh on every Overseer operation.
diff --git a/solr/core/src/java/org/apache/solr/search/grouping/distributed/responseprocessor/TopGroupsShardResponseProcessor.java b/solr/core/src/java/org/apache/solr/search/grouping/distributed/responseprocessor/TopGroupsShardResponseProcessor.java
index fa8de2428e7..d0a06c59d11 100644
--- a/solr/core/src/java/org/apache/solr/search/grouping/distributed/responseprocessor/TopGroupsShardResponseProcessor.java
+++ b/solr/core/src/java/org/apache/solr/search/grouping/distributed/responseprocessor/TopGroupsShardResponseProcessor.java
@@ -99,7 +99,7 @@ public class TopGroupsShardResponseProcessor implements ShardResponseProcessor {
 
         if (srsp.getException() != null) {
           Throwable t = srsp.getException();
-          if (t instanceof SolrServerException) {
+          if (t instanceof SolrServerException && ((SolrServerException) t).getCause() != null) {
             t = ((SolrServerException) t).getCause();
           }
           individualShardInfo.add("error", t.toString());