Index: applications/editors/josm/plugins/wmsplugin/src/wmsplugin/WMSLayer.java
===================================================================
--- applications/editors/josm/plugins/wmsplugin/src/wmsplugin/WMSLayer.java	(revision 13741)
+++ applications/editors/josm/plugins/wmsplugin/src/wmsplugin/WMSLayer.java	(revision 13796)
@@ -63,5 +63,5 @@
     protected final int serializeFormatVersion = 4;
 
-    private ExecutorService executor;
+    private ExecutorService executor = null;
 
     public WMSLayer() {
@@ -82,4 +82,11 @@
         
         executor = Executors.newFixedThreadPool(3);
+    }
+    
+    public void destroy() {
+        try { 
+            executor.shutdown();  
+        // Might not be initalized, so catch NullPointer as well
+        } catch(Exception x) {}
     }