Here is a better fix - update the childForm() function inside 'include.session.inc' from this:
if (isset($post['select'])) {
// convert selection into SQL where format
$pkey_array = $dbobject->getPkeyArray(null, $task_array);
$selection = selection2where($pkey_array, $post['select']);
} elseif (count($object_array) == 1 AND $pattern_id != 'LIST1') {
to this:
if (isset($post['select'])) {
if ($pattern_id == 'LIST2' AND $task_array['pattern_id'] == 'ADD2') {
// for LIST2->ADD2 any selection must be ignored
$selection = null;
} else {
// convert selection into SQL where format
$pkey_array = $dbobject->getPkeyArray(null, $task_array);
$selection = selection2where($pkey_array, $post['select']);
} // if
} elseif (count($object_array) == 1 AND $pattern_id != 'LIST1') {