Fix 'get_real_value' on placeholder nodes (#127698)
Summary:
X-link: https://github.com/pytorch/pytorch/pull/127698
Approved by: https://github.com/jansel
ghstack dependencies: #127695, #127696
Reviewed By: clee2000
Differential Revision: D58443884
fbshipit-source-id: 739dc15e745abc83691ee3bae3e29d8fd3bfa44a
