Attach the native entry struct to the ArchiveEntry object.

utils/archive/reader.dart

Index: utils/archive/reader.dart
diff --git a/utils/archive/reader.dart b/utils/archive/reader.dart
index 15ad75615a39fbf8ff78eed054af8f727fd55f9b..3a2830fecacb2828f2f96f7882a8ca35a9a1c10e 100644
--- a/utils/archive/reader.dart
+++ b/utils/archive/reader.dart
@@ -77,7 +77,7 @@ class ArchiveReader {
    * returns its id.
    */
   Future<int> _createArchive() {
-    return call(NEW, null).chain((id) {
+    return call(NEW).chain((id) {
       if (id == 0 || id == null) {
         throw new ArchiveException("Archive is invalid or closed.");
       }