Index: /trunk/src/org/openstreetmap/josm/actions/CombineWayAction.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/actions/CombineWayAction.java	(revision 16134)
+++ /trunk/src/org/openstreetmap/josm/actions/CombineWayAction.java	(revision 16135)
@@ -274,5 +274,6 @@
         if (ds == null)
             return;
-        Collection<Way> selectedWays = ds.getSelectedWays();
+        Collection<Way> selectedWays = new LinkedHashSet<>(ds.getSelectedWays());
+        selectedWays.removeIf(Way::isEmpty);
         if (selectedWays.size() < 2) {
             new Notification(