Handle null response metadata

Author: zoewangg

core/aws-core/src/main/java/software/amazon/awssdk/awscore/AwsResponseMetadata.java

@@ -18,6 +18,7 @@
 import static software.amazon.awssdk.awscore.util.AwsHeader.AWS_REQUEST_ID;
 
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
@@ -48,7 +49,7 @@ protected AwsResponseMetadata(Map<String, String> metadata) {
     }
 
     protected AwsResponseMetadata(AwsResponseMetadata responseMetadata) {
-        this(responseMetadata.metadata);
+            this(responseMetadata == null ? new HashMap<>() : responseMetadata.metadata);
     }
 
     /**

services/s3/src/main/java/software/amazon/awssdk/services/s3/internal/multipart/SdkPojoConversionUtils.java

@@ -131,13 +131,8 @@ public static CopyObjectResponse toCopyObjectResponse(CompleteMultipartUploadRes
 
         setSdkFields(builder, response);
 
-        if (response.responseMetadata() != null) {
-            builder.responseMetadata(response.responseMetadata());
-        }
-
-        if (response.sdkHttpResponse() != null) {
-            builder.sdkHttpResponse(response.sdkHttpResponse());
-        }
+        builder.responseMetadata(response.responseMetadata());
+        builder.sdkHttpResponse(response.sdkHttpResponse());
 
         return builder.copyObjectResult(toCopyObjectResult(response))
                       .build();
@@ -184,14 +179,8 @@ public static PutObjectResponse toPutObjectResponse(CompleteMultipartUploadRespo
 
         setSdkFields(builder, response);
 
-        // TODO: check why we have to do null check
-        if (response.responseMetadata() != null) {
-            builder.responseMetadata(response.responseMetadata());
-        }
-
-        if (response.sdkHttpResponse() != null) {
-            builder.sdkHttpResponse(response.sdkHttpResponse());
-        }
+        builder.responseMetadata(response.responseMetadata());
+        builder.sdkHttpResponse(response.sdkHttpResponse());
 
         return builder.build();
     }