Index: /applications/editors/josm/plugins/reverter/src/reverter/RevertChangesetAction.java
===================================================================
--- /applications/editors/josm/plugins/reverter/src/reverter/RevertChangesetAction.java	(revision 21236)
+++ /applications/editors/josm/plugins/reverter/src/reverter/RevertChangesetAction.java	(revision 21237)
@@ -31,8 +31,10 @@
     @Override
     protected void updateEnabledState() {
-        setEnabled(Main.main.getCurrentDataSet() != null);
+        setEnabled(getCurrentDataSet() != null);
     }
     
     public void actionPerformed(ActionEvent arg0) {
+        if (getCurrentDataSet() == null)
+            return;
         ChangesetIdQuery dlg = new ChangesetIdQuery();
         dlg.setVisible(true);