Check if those things are set.

(Perils of moving away from the loose `empty()`!)

src/LdapSyncCommand.php

@@ -1499,7 +1499,7 @@ private function deployGitlabUsersAndGroups(array $config, string $gitlabInstanc
                 continue;
             }
 
-            if ("" !== $usersSync["new"][$gitlabUserId]) {
+            if (isset($usersSync["new"][$gitlabUserId]) && "" !== $usersSync["new"][$gitlabUserId]) {
                 continue;
             }
 
@@ -1772,7 +1772,10 @@ private function deployGitlabUsersAndGroups(array $config, string $gitlabInstanc
         // Update groups of which were already in both Gitlab and the directory
         $this->logger?->notice("Updating groups of which were already in both Gitlab and the directory...");
         foreach ($groupsSync["found"] as $gitlabGroupId => $gitlabGroupName) {
-            if ("" !== $groupsSync["new"][$gitlabGroupId] || "" !== $groupsSync["extra"][$gitlabGroupId]) {
+            if (
+                (isset($groupsSync["new"][$gitlabGroupId]) && "" !== $groupsSync["new"][$gitlabGroupId])
+                || (isset($groupsSync["extra"][$gitlabGroupId]) && "" !== $groupsSync["extra"][$gitlabGroupId])
+            ) {
                 continue;
             }