Fix NPE in RelativeLayout.

    private View getRelatedView(int[] rules, int relation) {

        int id = rules[relation];

        if (id != 0) {

            View v = mGraph.mNodes.get(id).view;

            if (v == null) {

                return null;

            }

            DependencyGraph.Node node = mGraph.mNodes.get(id);

            if (node == null) return null;

            View v = node.view;

            // Find the first non-GONE view up the chain

            while (v.getVisibility() == View.GONE) {

                rules = ((LayoutParams) v.getLayoutParams()).getRules();

                v = mGraph.mNodes.get((rules[relation])).view;

                if (v == null) {

                    return null;

                }

                node = mGraph.mNodes.get((rules[relation]));

                if (node == null) return null;

                v = node.view;

            }

            return v;