Index: applications/editors/josm/plugins/mapillary/src/org/openstreetmap/josm/plugins/mapillary/MapillaryData.java
===================================================================
--- applications/editors/josm/plugins/mapillary/src/org/openstreetmap/josm/plugins/mapillary/MapillaryData.java	(revision 31988)
+++ applications/editors/josm/plugins/mapillary/src/org/openstreetmap/josm/plugins/mapillary/MapillaryData.java	(revision 31989)
@@ -76,4 +76,5 @@
    * @param image  The image to be added.
    * @param update Whether the map must be updated or not.
+   * @throws NullPointerException if parameter <code>image</code> is <code>null</code>
    */
   public synchronized void add(MapillaryAbstractImage image, boolean update) {
Index: applications/editors/josm/plugins/mapillary/src/org/openstreetmap/josm/plugins/mapillary/MapillaryLayer.java
===================================================================
--- applications/editors/josm/plugins/mapillary/src/org/openstreetmap/josm/plugins/mapillary/MapillaryLayer.java	(revision 31988)
+++ applications/editors/josm/plugins/mapillary/src/org/openstreetmap/josm/plugins/mapillary/MapillaryLayer.java	(revision 31989)
@@ -246,5 +246,7 @@
       img.setVisible(visible);
     }
-    MapillaryFilterDialog.getInstance().refresh();
+    if (Main.map != null) {
+      MapillaryFilterDialog.getInstance().refresh();
+    }
   }