Be able to disable the DHCP domain name

advanced/Scripts/webpage.sh

@@ -232,10 +232,13 @@ dhcp-authoritative
 dhcp-range=${DHCP_START},${DHCP_END},${leasetime}
 dhcp-option=option:router,${DHCP_ROUTER}
 dhcp-leasefile=/etc/pihole/dhcp.leases
-domain=${PIHOLE_DOMAIN}
 #quiet-dhcp
 " > "${dhcpconfig}"
 
+if [[ "${PIHOLE_DOMAIN}" != "none" ]]; then
+	echo "domain=${PIHOLE_DOMAIN}" >> "${dhcpconfig}"
+fi
+
 	if [[ "${DHCP_IPv6}" == "true" ]]; then
 echo "#quiet-dhcp6
 #enable-ra