added null check due to failing CI

Author: piergm

server/src/main/java/org/elasticsearch/search/internal/ShardSearchRequest.java

@@ -148,7 +148,7 @@ public ShardSearchRequest(
             numberOfShards,
             searchRequest.searchType(),
             searchRequest.source(),
-            searchRequest.source().query(),
+            (searchRequest.source() != null) ? searchRequest.source().query() : null,
             searchRequest.requestCache(),
             aliasFilter,
             indexBoost,