[BugFix] Check optional params before .get() call in gqa_rope_write_cache

[K11OntheBoat]

Motivation

在gqa_rope_write_cache中, 存在针对 为空的optional tensor 使用.get()方法的情况；导致Paddle框架Assert错误:
python: paddle/include/paddle/utils/optional.h:563: paddle::optional::reference_const_type paddle::optional::get() const [with T = paddle::Tensor; reference_const_type = const paddle::Tensor&]: Assertion `this->is_initialized()' failed.”

Modifications

此PR采用更标准的C++写法，用指针表示可选参数, 不存在的Optional不使用 .get()方法，参数用nullptr向下传入的方法，可以修复此Assertion报错.

[paddle-bot]

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[fastdeploy-bot]

🤖 AI Code Review | 2026-04-10

📋 Review 摘要

PR 概述：修复 gqa_rope_write_cache 中对空 optional tensor 使用 .get() 方法导致的 Assert 错误

变更范围：custom_ops/gpu_ops/append_attn/gqa_rope_write_cache.cu

影响面 Tag：[OP]

问题

级别	文件	概述
🟡 建议	代码整体	修复范围可能不完整，其他分支仍存在 .get() 调用

总体评价

PR 的修复思路和实现是正确的，通过将可选参数改为指针并使用三元运算符检查，有效避免了 optional tensor 为空时的 Assert 错误。但修复范围可能不完整，同一文件中 CascadeAppendWriteCacheKVC8QKV 和 CascadeAppendWriteCacheKVC4QKV 的调用处（行 1500-1525，不在本次 diff 范围内）仍使用 .get()，存在相同潜在问题。

建议确认这些调用路径是否也需要修复，或添加文档说明已知限制。

[fastdeploy-bot]

💡 设计说明：修复基于一个重要假设

当 cache_quant_type 不是 "none" 时，调用方必须提供相应的 optional tensor（如 cache_k_dequant_scales 等）。如果调用方未提供，当前代码会空指针解引用，行为未定义。

建议在 AppendCacheKV 函数开头添加参数验证，提供更清晰的错误信息。

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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