fix: dont do anything if there are no users

src/bin/update_groups.rs

@@ -88,6 +88,10 @@ async fn update_committee(config: &Config) -> tide::Result<()> {
 }
 
 async fn update_group(config: &Config, group: &str, users: &[&str], replace: bool) -> tide::Result<()> {
+    if users.is_empty() {
+        return Ok(());
+    }
+
     let mut ldap = LdapConn::new(&config.ldap_host)?;
 
     // use the admin account