fix(empty-state): Make sure inbox zero /always/ animates
fix(empty-state): Make sure inbox zero /always/ animates

- Animation plays on mount, so always unmount the empty state component instead
  of hiding it.

nylas-mail-lives/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas/nylas-mail