open PRs from external link: No error when no folder found

[aeschli]

Testing microsoft/vscode#274805

Open vscode-insiders://github.vscode-pull-request-github/checkout-pull-request?%7B%22owner%22%3A%22microsoft%22%2C%22repo%22%3A%22vscode-css-languageservice%22%2C%22pullRequestNumber%22%3A460%7D as external link

Nothing happens.

The Github Pull Request log shows: [UriHandler] No repository workspace found for https://github.com/microsoft/vscode-css-languageservice

Should show a info dialog that says that (and maybe ask me for the folder)

[Yoyokrazy]

✅