[AF iOS] Do not set angular model value for element without scope.

When elements don't have scope, setting the model value throws an
undefined element exceptions, causing autofill to fail.
Test existence of scope before updating model.

Bug: 846730
Change-Id: Ia1119604252829d2012bfc728de297607aa92883
Reviewed-on: https://chromium-review.googlesource.com/1072473Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562015}

components/autofill/ios/fill/resources/fill.js

@@ -178,14 +178,15 @@ function setInputElementAngularValue_(value, input) {
   }
   angular_element.val(value);
   var angular_model = angular_element.data && angular_element.data('ngModel');
-  if (!angular_model) {
+  var angular_scope = angular_element.scope();
+  if (!angular_model || !angular_scope) {
     return;
   }
   angular_element.injector().invoke([
     '$parse',
     function(parse) {
       var setter = parse(angular_model);
-      setter.assign(angular_element.scope(), value);
+      setter.assign(angular_scope, value);
     }
   ]);
 }