When there is no VRF/upper interface the script will produce the following error:
Oct 20 11:59:49 vyos dhclient[2057]: /etc/dhcp/dhclient-exit-hooks.d/01-vyos-cleanup: line 25: [: too many arguments
as in that situation $vrf_name will evaluate to * and then be expanded to a list of files/directories in the working directory of the script.