• Extension version: v0.85.2024032704 (pre-release)
• VSCode Version:
  1.88.0-insider (user setup)
  Commit: aa25485166449aa0f9eb8ebd8d0b70376108633c
  Date: 2024-03-28T22:10:25.599Z
• OS: Windows
• Repository Clone Configuration (single repository/fork of an upstream repository): https://github.com/microsoft/vscode-markdown-it-katex, which is forked from an upstream repository.

Steps to Reproduce:

1. Clone https://github.com/microsoft/vscode-markdown-it-katex locally
2. Create a PR using the extension. The extension automatically sets the base to iktakahiro/markdown-it-katex/master.
3. Change the base repository to the microsoft one, and select the main branch.
4. 🐛 The viewlet clears itself. A workaround is closing and reopening the sidebar.