Index: /applications/editors/josm/plugins/validator/build.xml
===================================================================
--- /applications/editors/josm/plugins/validator/build.xml	(revision 19223)
+++ /applications/editors/josm/plugins/validator/build.xml	(revision 19224)
@@ -26,5 +26,5 @@
 	  ** update before publishing 
 	-->
-	<property name="commit.message" value="Updated to JOSM 2621" />
+	<property name="commit.message" value="Fixed JOSM ticket #4235 - Validation layer is not removed when data layers are removed" />
 	<property name="plugin.main.version" value="2621" />
 
Index: /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/OSMValidatorPlugin.java
===================================================================
--- /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/OSMValidatorPlugin.java	(revision 19223)
+++ /applications/editors/josm/plugins/validator/src/org/openstreetmap/josm/plugins/validator/OSMValidatorPlugin.java	(revision 19224)
@@ -14,6 +14,4 @@
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.Iterator;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -291,4 +289,7 @@
     }
 
+    /* -------------------------------------------------------------------------- */
+    /* interface LayerChangeListener                                              */
+    /* -------------------------------------------------------------------------- */
     public void activeLayerChange(Layer oldLayer, Layer newLayer) {
         if (newLayer instanceof OsmDataLayer) {
@@ -306,5 +307,14 @@
 
     public void layerRemoved(Layer oldLayer) {
+    	if (oldLayer == errorLayer) {
+    		errorLayer = null;
+    		return;
+    	}
         layerErrors.remove(oldLayer);
+        if (Main.map.mapView.getLayersOfType(OsmDataLayer.class).isEmpty()) {
+        	if (errorLayer != null) {
+        		Main.map.mapView.removeLayer(errorLayer);
+        	}
+        }
     }
 }