Prevent array out of bound access

Summary:
Even so the problem of #236 has been fixed via ced779b there is still a case where you have a out of bound array access of undefined behaviour. This PR prevents the out of bound access of the underlying c array. The out of bound access happens if you already have 4 subViews and add another one. Then you will access CSSNodeGetChild with 4 which points into uninitialized memory.
Closes https://github.com/facebook/css-layout/pull/237

Reviewed By: dshahidehpour

Differential Revision: D4107743

Pulled By: emilsjolander

fbshipit-source-id: 0f21397f3a77308369acfea7327733f74eb72e00

uikit/CSSLayout/UIView+CSSLayout.m

@@ -250,7 +250,7 @@ static void _attachNodesRecursive(UIView *view) {
     // Add any children which were added since the last call to css_applyLayout
     for (NSUInteger i = 0; i < view.subviews.count; i++) {
       CSSNodeRef childNode = [view.subviews[i] cssNode];
-      if (CSSNodeGetChild(node, i) != childNode) {
+      if (CSSNodeChildCount(node) < i + 1 || CSSNodeGetChild(node, i) != childNode) {
         CSSNodeInsertChild(node, childNode, i);
       }
       _attachNodesRecursive(view.subviews[i]);