git_ui: Fix creating worktree not possible if default branch unavailable (#57918)

Follow up to #57704

This makes sure that we offer a worktree creation option in case
resolving the default branch fails

Release Notes:

- git: Fixed an issue where worktree creation would not be possible if
resolving default branch fails
d74e47ea51Bennet Bo Fenner committed on 5/28/2026, 2:15:40 PM· committed by GitHubparentf0ed342
1 file changedLine totals unavailable