Debugging untitled file non-workspace window hangs due to cwd being set incorrectly

[daviwil]

Steps:

1. Open VS Code without a workspace path (don't load a folder)
2. Create a new file with Ctrl+N and set its language mode to PowerShell
3. Write Get-Process in the file
4. Press F5
5. Debugger hangs, logs complain about setting cwd with path of untitled:Untitled-1