Index: applications/editors/josm/plugins/utilsplugin/src/UtilsPlugin/JoinAreasAction.java
===================================================================
--- applications/editors/josm/plugins/utilsplugin/src/UtilsPlugin/JoinAreasAction.java	(revision 13723)
+++ applications/editors/josm/plugins/utilsplugin/src/UtilsPlugin/JoinAreasAction.java	(revision 13776)
@@ -236,5 +236,6 @@
 
         // Delete the remaining inner ways
-        cmds.add(DeleteCommand.delete(innerWays, true));
+        if(innerWays != null && innerWays.size() > 0)
+            cmds.add(DeleteCommand.delete(innerWays, true));
         commitCommands("Delete Ways that are not part of an inner multipolygon");