Index: /trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 5108)
+++ /trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 5109)
@@ -534,5 +534,5 @@
         String key = keys.getEditor().getItem().toString().trim();
         String value = values.getEditor().getItem().toString().trim();
-        if (value.equals(""))
+        if (key.isEmpty() || value.isEmpty())
             return;
         lastAddKey = key;