Newer versions of project.el changed the return value of
`project-current` to a three-part list, rather than a cons cell.
centaur-tabs expects the old signature and we get a type error.
This advice ensures centaur-tabs works with old or new versions of
project, and is a temporary measure until the issue is resolved
upstream.
Ref: ema2159/centaur-tabs#181
Fix: #6280
8b93e8b15c