Update multipolygon action no longer works (since JOSM 12914)

[sebastic]

Since JOSM 12914 the 'Update multipolygon' action no longer works.

Selecting the (only) outer way and the relation, and then using Ctrl+Shift+B or the menu option does not perform any action (nothing logged in debug mode on the console either).

The 'Create multipolygon' action still works.

SVN r12726 looks like a possible culprit where this change was committed to src/org/openstreetmap/josm/actions/CreateMultipolygonAction.java:

@@ -247,7 +247,7 @@ public class CreateMultipolygonAction extends JosmAction {
         final List<Command> list = removeTagsFromWaysIfNeeded(relation);
         final String commandName;
         if (existingRelation == null) {
-            list.add(new AddCommand(relation));
+            list.add(new AddCommand(selectedWays.iterator().next().getDataSet(), relation));
             commandName = getName(false);
         } else {
             list.add(new ChangeCommand(existingRelation, relation));

The other changes to CreateMultipolygonAction.java seem to be pretty harmless Config.getPref() changes, and my prefs match the default values.

Perhaps the ChangeCommand needs to pass the Dataset too?