Index: /applications/editors/josm/plugins/walkingpapers/src/org/openstreetmap/josm/plugins/walkingpapers/WalkingPapersAddLayerAction.java
===================================================================
--- /applications/editors/josm/plugins/walkingpapers/src/org/openstreetmap/josm/plugins/walkingpapers/WalkingPapersAddLayerAction.java	(revision 16567)
+++ /applications/editors/josm/plugins/walkingpapers/src/org/openstreetmap/josm/plugins/walkingpapers/WalkingPapersAddLayerAction.java	(revision 16568)
@@ -29,4 +29,6 @@
         	tr("Enter a walking-papers.org URL or ID (the bit after the ?id= in the URL)"),
         		Main.pref.get("walkingpapers.last-used-id"));
+
+        if (wpid == null || wpid.equals("")) return;
 
         // Grab id= from the URL if we need to, otherwise get an ID