patch: Don't chock if cert. chain is missing

> this condition is valid where a default cert. isn't issued (.CN == {{tld}}` (e.g. `api.{{tld}}` but not `{{tld}}`)

https://balena.fibery.io/Work/Project/Anton-works-1422

Author: ab77

entry.sh

@@ -710,7 +710,7 @@ touch "${CERTS}/.ready"
 remove_update_lock
 
 while true; do
-	check_cert_expiry "${EXPORT_CERT_CHAIN_PATH}"
-	check_self_signed_certs_expiry
+	[[ -s "$EXPORT_CERT_CHAIN_PATH" ]] && check_cert_expiry "${EXPORT_CERT_CHAIN_PATH}"  # cert. chain may not exist (by design)
+	check_self_signed_certs_expiry  # .. but at least some self-signed certs. should
 	sleep 1d
 done