x unbound variable

Question

I am trying to run that script here:

#!/bin/bash
set -o errexit # be strong with errors
set -o nounset # be strong with unset vars
PROG="${0##/}" # Scriptname
USAGE="usage: $PROG clientname"
EASYRSA="EasyRSA-<VERSION>"
CA_SERVER="user@my-CA-server"
VPN_SERVER="<IP-Address of the openvpn server>"
VPN_SERVER_PORT="1194"
ZIP=/usr/bin/zip
if! -x $ZIP; then
echo "${PROG}: $ZIP not found, install it first" >&2
exit 1
fi
if (( $# != 1 )) ; then
echo $USAGE
exit 1
fi
if! -d $EASYRSA; then
echo "$EASYRSA missing or wrong version" >&2
exit 1
fi
CLIENT=$1
CLIENTCONFIG=$HOME/${CLIENT}-vpnconfig # define directory for config
echo "-----------------------------------------------------------------------------------------"
echo "
This script generates the keys/certs and a config file for your connetion to the openVPN
server.
EasyRSA is: $EASYRSA
CA-Server (PKI) is: $CA_SERVER
openVPN server is: $VPN_SERVER
Build a config for: $CLIENT
Config built in: $CLIENTCONFIG
NOTE: you need a working ssh-connection between your $VPN_SERVER and the $CA_SERVER!
If that's not what you want, hit ^C. Hit <ENTER> if that's OK
"
read OK
-d ${CLIENTCONFIG}|| mkdir -pm 700 ${CLIENTCONFIG}
echo "generate the request"
cd ~/$EASYRSA
./easyrsa gen-req $CLIENT nopass
cp pki/private/${CLIENT}.key ${CLIENTCONFIG}
echo "secure copy the req to the CA-server"
scp pki/reqs/${CLIENT}.req $CA_SERVER:/tmp && stat=$? || stat=$?
case $stat in
0) ;; # all fine
*) echo "$PROG: scp to $CA_SERVER failed" >&2
exit 1
;;
esac
echo "Login to your CA-server and import/sign the request"
ssh -T $CA_SERVER "cd $EASYRSA;./easyrsa import-req /tmp/${CLIENT}.req $CLIENT;./easyrsa sign-req client $CLIENT" && stat=$? || stat=$?
case $stat in
0) ;; # all fine
*) echo "$PROG: scp to $CA_SERVER failed" >&2
exit 1
;;
esac
echo "Copy the ${CLIENT}.crt from your CA-Server to your local ${CLIENTCONFIG} directory."
scp ${CA_SERVER}:${EASYRSA}/pki/issued/${CLIENT}.crt ${CLIENTCONFIG}
cp ta.key ${CLIENTCONFIG}
echo "Copy the ca.crt (CA certificate) into your ${CLIENTCONFIG} directory"
scp root@${CA_SERVER}:/etc/openvpn/ca.crt ${CLIENTCONFIG}
cd $CLIENTCONFIG
echo -n "Create the ${CLIENT}.ovpn file now"
cat > ${CLIENTCONFIG}/${CLIENT}.ovpn << EdF
client
dev tun
persist-key
persist-tun
proto udp
nobind
remote-cert-tls server
auth SHA512
verb 3
remote ${VPN_SERVER} ${VPN_SERVER_PORT}
To successfully import this profile, you
want the client device's CA certificate copy,
client certificate and key, and HMAC signature
all in the same location as this .ovpn file.
ca ca.crt
cert ${CLIENT}.crt
key ${CLIENT}.key
tls-crypt ta.key
EdF
echo " done"
if-f ca.crt&&-f ${CLIENT}.crt&&
 -f ${CLIENT}.key&&-f ta.key&&-f ${CLIENT}.ovpn; then
echo -n "Your kit seems complete. Will create ${CLIENT}.zip"
zip -r ${CLIENT}-openvpn.zip ${CLIENT}.ovpn ${CLIENT}.crt ${CLIENT}.key ca.crt ta.key
echo " done"
else
echo "you miss some files" >&2
exit 1
fi
exit 0

to generate my client certificates. It gives me a syntax error at line 13. So I changed that line to:

if (( ! -x $ZIP ))  ; then

Now I get an error: x unbound variable. How do I have to write that line correctly?

Many thanks in advance,

Uli