Remove _legacyUndefinedCheck

Change-Id: I30ce336c0dccc3c31f99403c1f2a1296210b38ba
diff --git a/src/main/resources/static/zuul-status-view.js b/src/main/resources/static/zuul-status-view.js
index 3c8575c..4d0c3e2 100644
--- a/src/main/resources/static/zuul-status-view.js
+++ b/src/main/resources/static/zuul-status-view.js
@@ -60,7 +60,6 @@
 
   Polymer({
     is: 'zuul-status-view',
-    _legacyUndefinedCheck: true,
 
     properties: {
       zuulUrl: String,