Adjust ridx if mrb_yield terminated by break; fix #3686

This issue is related to #3640.

src/vm.c

@@ -283,8 +283,8 @@ cipop(mrb_state *mrb)
   struct mrb_context *c = mrb->c;
   struct REnv *env = c->ci->env;
 
+  c->ridx = c->ci->rpos;
   c->ci--;
-
   if (env) {
     mrb_env_unshare(mrb, env);
   }