bug 115159, fix event firing for radiogroups

r=brendan
sr=blake
a=asa

xpfe/global/resources/content/bindings/radio.xml

@@ -75,7 +75,7 @@
 
           var myEvent = document.createEvent("Events");
           myEvent.initEvent("RadioStateChange", true, true);
-          this.selectedItem.dispatchEvent(myEvent);
+          val.dispatchEvent(myEvent);
 
           return val;
         ]]>