[VSCode Plugin] 在 workspace 下没有 `*.md` 文档时不能正确预览

[RSS1102]

Validations

• [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Issue Type

Feature Request

Version

v0.0.18

Clear and concise description of the problem or idea.

如果使用 vscode 直接打开 一个 *.md 文件进行预览(在右侧 workspace 没有 *.md 文件) 则不能正确预览。

Additional context

No response

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