Mark as modified when default is a list of ids

Otherwise they are not sent to the server because only modified record are
sent since issue6754.

issue9479
review308441002

src/model.js

@@ -2119,7 +2119,7 @@
                         group.remove(old_record, true, true, false, false);
                     }
                 }
-                group.load(value, modified);
+                group.load(value, modified || default_);
             } else {
                 value.forEach(function(vals) {
                     var new_record = group.new_(false);