fix: panic: assignment to entry in nil map on S3Sink.CreateEntry (#5406)

weed/replication/sink/s3sink/s3_sink.go

@@ -175,19 +175,24 @@ func (s3sink *S3Sink) CreateEntry(key string, entry *filer_pb.Entry, signatures
 			uploader.PartSize = 0
 		}
 	}
-	if _, ok := entry.Extended[s3_constants.AmzUserMetaMtime]; !ok {
+
+	doSaveMtime := true
+	if entry.Extended == nil {
+		entry.Extended = make(map[string][]byte)
+	} else if _, ok := entry.Extended[s3_constants.AmzUserMetaMtime]; ok {
+		doSaveMtime = false
+	}
+	if doSaveMtime {
 		entry.Extended[s3_constants.AmzUserMetaMtime] = []byte(strconv.FormatInt(entry.Attributes.Mtime, 10))
 	}
 	// process tagging
 	tags := ""
-	if true {
 	for k, v := range entry.Extended {
 		if len(tags) > 0 {
 			tags = tags + "&"
 		}
 		tags = tags + k + "=" + string(v)
 	}
-	}
 
 	// Upload the file to S3.
 	uploadInput := s3manager.UploadInput{