diff --git a/src/CustomString/widget/CustomString.js b/src/CustomString/widget/CustomString.js
index cb061d6..f7dd6e2 100644
--- a/src/CustomString/widget/CustomString.js
+++ b/src/CustomString/widget/CustomString.js
@@ -67,6 +67,10 @@ define([
 
         _updateRendering : function (callback) {
             logger.debug(this.id + "._updateRendering");
+            if ( this._contextObj == null || typeof this._contextObj == "undefined" ) {
+                this._executeCallback(callback, "_updateRendering emptyObject");
+                return;
+            }
             mx.ui.action(this.sourceMF, {
                 params: {
                     applyto     : "selection",