https://gitlab.com/gitlab-org/security/gitlab-workhorse/-/merge_requests/3
changed Workhorse so that it always provided `file.path` when
`direct_upload` was enabled, even if that path was blank.

Whereas we were checking for `path` not being `nil`, we now need to
check that it's present.

See also https://gitlab.com/gitlab-org/gitlab/-/issues/212424