If the ctr.path is empty, then we do not try to access
`/sys/fs/cgroup/pids/pids.current` any more because this path will be
wrong in any case. We now return and do not set the PIDs stats.
Refers to https://github.com/cri-o/cri-o/issues/3522
Signed-off-by: Sascha Grunert <sgrunert@suse.com>