Index: /trunk/src/org/openstreetmap/josm/gui/dialogs/ValidatorDialog.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/dialogs/ValidatorDialog.java	(revision 14886)
+++ /trunk/src/org/openstreetmap/josm/gui/dialogs/ValidatorDialog.java	(revision 14887)
@@ -219,9 +219,12 @@
         void updateEnabledState() {
             boolean found = false;
-            for (TestError e : tree.getErrors()) {
-                for (OsmPrimitive p : e.getPrimitives()) {
-                    if (p.isSelected()) {
-                        found = true;
-                        break;
+            final DataSet ds = MainApplication.getLayerManager().getActiveDataSet();
+            if (ds != null && !ds.selectionEmpty()) {
+                for (TestError e : tree.getErrors()) {
+                    for (OsmPrimitive p : e.getPrimitives()) {
+                        if (p.isSelected()) {
+                            found = true;
+                            break;
+                        }
                     }
                 }