Fix iOS8 Mobile Safari bug

This bug manifested itself intermittently but reliably on the lite race page when navigating between races using the race selector.

```
Error: Attempted to assign to readonly property.
$new@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:5:17358
https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:6:24621
forEach@[native code]
o@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:3:36207
https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:6:24594
$digest@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:5:19046
$apply@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:5:20575
l@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:4:60979
b@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:4:47052
onreadystatechange@https://lite.tab.com.au/assets/application-929d654fa27854db6faf6d91b698eb47.js:4:47628
```

The root cause is believed to be this bug in Webkit:

https://bugs.webkit.org/show_bug.cgi?id=49739

The fix appeared in this issue in angular.js:

angular/angular.js#9128

Author: Josh Price

angular.js

@@ -11984,21 +11984,21 @@ function $RootScopeProvider(){
           // Only create a child scope class if somebody asks for one,
           // but cache it to allow the VM to optimize lookups.
           if (!this.$$childScopeClass) {
-            this.$$childScopeClass = function() {
-              this.$$watchers = this.$$nextSibling =
-                  this.$$childHead = this.$$childTail = null;
-              this.$$listeners = {};
-              this.$$listenerCount = {};
-              this.$id = nextUid();
-              this.$$childScopeClass = null;
+            this['$$childScopeClass'] = function() {
+              this['$$watchers'] = this['$$nextSibling'] =
+                  this['$$childHead'] = this['$$childTail'] = null;
+              this['$$listeners'] = {};
+              this['$$listenerCount'] = {};
+              this['$id'] = nextUid();
+              this['$$childScopeClass'] = null;
             };
             this.$$childScopeClass.prototype = this;
           }
           child = new this.$$childScopeClass();
         }
         child['this'] = child;
-        child.$parent = this;
-        child.$$prevSibling = this.$$childTail;
+        child['$parent'] = this;
+        child['$$prevSibling'] = this.$$childTail;
         if (this.$$childHead) {
           this.$$childTail.$$nextSibling = child;
           this.$$childTail = child;