Link from a uses: with unspecified version goes to tree/undefined

**Describe the bug**
When writing `uses: actions/checkout` in a file, ctrl + clicking it to open in web browser opens it to github.com/actions/checkout/tree/undefined

**To Reproduce**
1. Create workflow with `uses: actions/checkout` in a step
2. ctrl + click it to go to github
3. 404 page as there is no undefined tag

**Expected behavior**
It should go to the repository main page

**Extension Version**
`v0.27.2`

**Additional context**
It would be cool to know the latest version of that module in the highlight.

首先，使用包含 `uses: actions/checkout` 的 workflow 步骤复现 ctrl-click 行为，然后跟踪对未指定版本的链接处理。完成的标准是链接打开 repository 主页面，而不是打开包含 `tree/undefined` 的 URL；分别考虑扩展版本和突出显示最新版本的请求。

由索引模型根据 Issue 内容生成。