fixed #17016: wrong assertion if label is empty and uses BitmapFont

[dumganhar]

Re: #17016

Also reported at https://forum.cocos.org/t/topic/160454/17

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.

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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.

[dumganhar]

@cocos-robot run test cases

[github-actions]

⚠️ Package size ⤴ 26 bytes, old: 5441175, new: 5441201

Interface Check Report

! WARNING this pull request has changed these public interfaces:

@@ -61475,12 +61475,12 @@
             protected _nativeObj: _cocos_2d_renderer_native_2d__NativeRenderDrawInfo;
             protected _uint8SharedBuffer: Uint8Array;
             protected _uint16SharedBuffer: Uint16Array;
             protected _uint32SharedBuffer: Uint32Array;
-            protected _render2dBuffer: Float32Array;
+            protected _render2dBuffer: Float32Array | null;
             constructor(nativeDrawInfo?: _cocos_2d_renderer_native_2d__NativeRenderDrawInfo);
             get nativeObj(): _cocos_2d_renderer_native_2d__NativeRenderDrawInfo;
-            get render2dBuffer(): Float32Array;
+            get render2dBuffer(): Float32Array | null;
             clear(): void;
             setAccId(accId: any): void;
             setBufferId(bufferId: any): void;
             setAccAndBuffer(accId: any, bufferId: any): void;

[dumganhar]

@cocos-robot run test cases

[AkshayshettyS]

Does this fix this issue - https://forum.cocosengine.org/t/force-updating-label-with-cache-mode-char-gives-error-in-debug-mode/61098

[dumganhar]

@AkshayshettyS Yes, it seems to be the same issue.

[dumganhar]

@cocos-robot run test cases

[dumganhar]

PR test run on windows PASS: https://github.com/cocos/cocos-engine/actions/runs/12270410220/job/34235569995