"Copy Relative Path" action had a check for existence of relative path
but it always passed because
[`WorktreeStore::find_worktree()`](https://github.com/zed-industries/zed/blob/1d5499bee72f1ea57ed883b942f05d5c1e7cec89/crates/project/src/worktree_store.rs#L148)
function returned empty path for these kinds of files. It feels correct
to make changes there, but I don't know what else could be impacted.

"Reveal In Project Panel" had no check whatsoever and so I made one.

Release Notes:

- N/A