? openlayers-empty-wtk.patch
Index: includes/behaviors/js/openlayers_behavior_drawfeatures.js
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/openlayers/includes/behaviors/js/Attic/openlayers_behavior_drawfeatures.js,v
retrieving revision 1.1.2.15
diff -u -p -r1.1.2.15 openlayers_behavior_drawfeatures.js
--- includes/behaviors/js/openlayers_behavior_drawfeatures.js	26 Aug 2010 16:23:52 -0000	1.1.2.15
+++ includes/behaviors/js/openlayers_behavior_drawfeatures.js	23 Sep 2010 11:02:25 -0000
@@ -26,7 +26,9 @@ Drupal.behaviors.openlayers_behavior_dra
         new OpenLayers.Projection("EPSG:4326")
       );
     }
-    this.element.val(WktWriter.write(features_copy.features));
+    if (features_copy.features.length >= 1 ) {
+      this.element.val(WktWriter.write(features_copy.features));
+    }
   }
 
   var data = $(context).data('openlayers');