I ran into a case locally where the project diff view was unexpectedly
empty because the first file to be scanned wasn't valid UTF-8, and the
inmost loop in `schedule_worktree_rescan` currently breaks when any
loading task fails. It seems like it might make more sense to continue
with the rest of the buffers in this case and also when
`Project::open_unstaged_changes` fails. I've left the error handling for
`update` as-is.
Release Notes:
- Fix project diff view missing files
c5b6d78d5b