Fix user group dropdown condition

Author: cedric-anne

Diff for: src/Group_User.php

@@ -205,7 +205,14 @@ public static function showForUser(User $user)
                 'condition' => [
                     'is_usergroup' => 1,
                 ] + getEntitiesRestrictCriteria(Group::getTable(), '', '', true)
-            ] + ['NOT' => self::getListForItemParams($user)];
+            ];
+
+            if (count($used) > 0) {
+                $params['condition'][] = [
+                    'NOT' => [Group::getTable() . '.id' => $used]
+                ];
+            }
+
             Group::dropdown($params);
             echo "</td><td>" . _n('Manager', 'Managers', 1) . "</td><td>";
             Dropdown::showYesNo('is_manager');