don't stop block variable scope finding on first hit

lib/6to5/traverse/scope.js

@@ -170,9 +170,8 @@ var blockVariableVisitor = {
   enter: function (node, parent, scope, context, add) {
     if (t.isBlockScoped(node)) {
       add(node, false, true);
-      context.stop();
     } else if (t.isScope(node)) {
-      context.skip();
+      context.stop();
     }
   }
 };