Fix crash of login in case of duplicated group membership

If several LDAP configurations return the same group id for a user it
 should still only appear once in the return of getUserGroups

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

apps/user_ldap/lib/Group_Proxy.php

@@ -178,7 +178,7 @@ class Group_Proxy extends Proxy implements \OCP\GroupInterface, IGroupLDAP, IGet
 			}
 		}
 
-		return $groups;
+		return array_values(array_unique($groups));
 	}
 
 	/**