解决 _entity 为空时 ,引起的闪退

[finscn]

关联 bug #18560 .

这个 pr 只是解决我遇到的问题.
但是还可能有其他问题, 比如

• 我看其他动画相关的cpp类里, 也有类似逻辑 ( 使用了 setRenderEntity() 和 _entity ) , 是否也应该加上同样的判断?
• 一个动画已经被销毁了, 为什么还会调用它的 render 方法? 是否有更深层的 bug 没有被发现?

这些问题就留给引擎组的同学去解决吧 我个人能力有限.帮不上忙.

Re: #

Changelog

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Continuous Integration

This pull request:

• needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

---

Compatibility Check

This pull request:

• changes public API, and have ensured backward compatibility with deprecated features.
• affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• affects file structure of the build package or build configuration which requires user project upgrade.
• introduces breaking changes, please list all changes, affected features and the scope of violation.

[github-actions]

Code Size Check Report

Wechat (WASM)	Before	After	Diff
2D Empty (legacy pipeline)	1002433 bytes	1002433 bytes	✅ 0 bytes
2D All (legacy pipeline)	2664474 bytes	2664474 bytes	✅ 0 bytes
2D All (new pipeline)	2752682 bytes	2752682 bytes	✅ 0 bytes
(2D + 3D) All	10005962 bytes	10005962 bytes	✅ 0 bytes

Web (WASM + ASMJS)	Before	After	Diff
(2D + 3D) All	16919743 bytes	16919743 bytes	✅ 0 bytes

Interface Check Report

This pull request does not change any public interfaces !

[finscn]

3.8.5 没有闪退是因为 3.8.5 里没有 清空 _entity

[bofeng-song]

请描述复现步骤，上传复现demo

[bofeng-song]

@finscn 请参考这个 PR；当前的改动不够完整，我先关闭了