Fix amp with optiontional api bug

[zhangbo9674]

PR types

Bug fixes

PR changes

APIs

Describe

修复最终态api amp与optional类型tensor组合使用的代码bug.

optional 类 tensor 的amp逻辑如下：

// const paddle::optional<const paddle::experimental::Tensor&> prior_dist
if (egr::Controller::Instance().GetAMPLevel() != paddle::imperative::AmpLevel::O0) {
        ...
        if (prior_dist.get_ptr() != nullptr) amp_tensors_vector.push_back({ *(prior_dist.get_ptr()) });
        ...
        auto NEW_prior_dist = (prior_dist.get_ptr() != nullptr) ? paddle::make_optional<const paddle::experimental::Tensor&>(egr::EagerAmpAutoCast("prior_dist", *(prior_dist.get_ptr()), amp_dst_dtype, op_name)) : prior_dist;
       ...
    }