Check ETag AtomicReference value not its reference

src/main/java/org/gaul/s3proxy/S3ProxyHandler.java

@@ -2352,7 +2352,7 @@ public class S3ProxyHandler {
             writeSimpleElement(xml, "Bucket", containerName);
             writeSimpleElement(xml, "Key", blobName);
 
-            if (eTag != null) {
+            if (eTag.get() != null) {
                 writeSimpleElement(xml, "ETag", maybeQuoteETag(eTag.get()));
             }