Index: trunk/src/org/openstreetmap/josm/data/imagery/ImageryLayerInfo.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/imagery/ImageryLayerInfo.java	(revision 11689)
+++ trunk/src/org/openstreetmap/josm/data/imagery/ImageryLayerInfo.java	(revision 11690)
@@ -273,4 +273,8 @@
         List<String> drop = new ArrayList<>();
 
+        if (defaultLayerIds.isEmpty()) {
+            return;
+        }
+        
         for (Map.Entry<String, ImageryInfo> info : layerIds.entrySet()) {
             if (!defaultLayerIds.containsKey(info.getKey())) {