Index: /trunk/src/org/openstreetmap/josm/data/osm/DataSet.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/osm/DataSet.java	(revision 18199)
+++ /trunk/src/org/openstreetmap/josm/data/osm/DataSet.java	(revision 18200)
@@ -388,5 +388,9 @@
      */
     public void addChangeSetTag(String k, String v) {
-        this.changeSetTags.put(k, v);
+        if (v != null) {
+            this.changeSetTags.put(k, v);
+        } else {
+            this.changeSetTags.remove(k);
+        }
     }
 
Index: /trunk/src/org/openstreetmap/josm/io/remotecontrol/handler/LoadAndZoomHandler.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/io/remotecontrol/handler/LoadAndZoomHandler.java	(revision 18199)
+++ /trunk/src/org/openstreetmap/josm/io/remotecontrol/handler/LoadAndZoomHandler.java	(revision 18200)
@@ -255,5 +255,11 @@
                     for (String tag : Arrays.asList("changeset_comment", "changeset_source", "changeset_hashtags")) {
                         if (args.containsKey(tag)) {
-                            ds.addChangeSetTag(tag.substring("changeset_".length()), args.get(tag));
+                            final String tagKey = tag.substring("changeset_".length());
+                            final String value = args.get(tag);
+                            if (!Utils.isStripEmpty(value)) {
+                                ds.addChangeSetTag(tagKey, value);
+                            } else {
+                                ds.addChangeSetTag(tagKey, null);
+                            }
                         }
                     }