avoiding NPEs

Author: masseyke

modules/data-streams/src/main/java/org/elasticsearch/datastreams/action/PutDataStreamSettingsTransportAction.java

@@ -247,7 +247,11 @@ private void updateSettingsOnIndices(
             // Called when all indices for all settings are complete
             @Override
             public void onResponse(Void unused) {
-                DataStream dataStream = clusterService.state().projectState(projectResolver.getProjectId()).metadata().dataStreams().get(dataStreamName);
+                DataStream dataStream = clusterService.state()
+                    .projectState(projectResolver.getProjectId())
+                    .metadata()
+                    .dataStreams()
+                    .get(dataStreamName);
                 listener.onResponse(
                     new PutDataStreamSettingsAction.DataStreamSettingsResponse(
                         dataStreamName,

server/src/main/java/org/elasticsearch/cluster/metadata/DataStream.java

@@ -380,7 +380,7 @@ public static ComposableIndexTemplate mergeSettingsIntoTemplate(ComposableIndexT
 
     private static Settings mergeSettings(Settings originalSettings, Settings newSettings) {
         if (Settings.EMPTY.equals(newSettings)) {
-            return originalSettings;
+            return Objects.requireNonNullElse(originalSettings, Settings.EMPTY);
         }
         Settings.Builder settingsBuilder = Settings.builder().put(originalSettings).put(newSettings);
         for (String settingName : new HashSet<>(settingsBuilder.keys())) {