Fix NPE due to missing params set during serialization

Author: lukewhiting

server/src/main/java/org/elasticsearch/action/bulk/BulkRequest.java

@@ -48,6 +48,7 @@
 import java.util.Objects;
 import java.util.Set;
 
+import static java.util.Collections.emptySet;
 import static org.elasticsearch.action.ValidateActions.addValidationError;
 
 /**
@@ -86,7 +87,7 @@ public class BulkRequest extends LegacyActionRequest
     private Boolean globalRequireAlias;
     private Boolean globalRequireDatsStream;
     private boolean includeSourceOnError = true;
-    private Set<String> paramsUsed;
+    private Set<String> paramsUsed = emptySet();
 
     private long sizeInBytes = 0;
 

server/src/main/java/org/elasticsearch/action/bulk/TransportAbstractBulkAction.java

@@ -48,7 +48,6 @@
 import org.elasticsearch.transport.TransportService;
 
 import java.io.IOException;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
@@ -486,10 +485,7 @@ private void doStreamsChecks(
     }
 
     private boolean streamsRestrictedParamsUsed(BulkRequest bulkRequest) {
-        return Sets.difference(
-            bulkRequest.requestParamsUsed() == null ? Collections.emptySet() : bulkRequest.requestParamsUsed(),
-            STREAMS_ALLOWED_PARAMS
-        ).isEmpty() == false;
+        return Sets.difference(bulkRequest.requestParamsUsed(), STREAMS_ALLOWED_PARAMS).isEmpty() == false;
     }
 
     /**