A better steINterval call maybe ?

templates/feedbackform.html

@@ -145,7 +145,7 @@
             $('#step5').removeClass('green').removeClass('outline_green').addClass('red');
             $('#step6').removeClass('green').removeClass('outline_green').addClass('red');
             $('#callee').removeClass('green').removeClass('outline_green').addClass('red');
-            clearInterval(window.interval);
+            window.clearInterval(window.interval);
         }
         console.log(call_state[0]);
     };