fix: ignore empty domain names

certbotd.sh

@@ -108,6 +108,11 @@ case $1 in
         if test -s "${cert}"; then
           domain="`certtool -i < "${cert}" | grep Subject: | cut -d = -f 2 | tr -d " "`"
 
+          if test -z "${domain}" ; then
+            not_ok "couldn't find domain name for certificate ${cert}"
+            continue
+          fi
+
           if grep -q "^${domain}$" "${domains}"; then
             echo "ok - ${domain} certificate correctly set"
           else