"Masquerade as" Field not working as expected

As I'm pretty new to drupal, I'm not sure if this is the right thing to do but I fixed this on my site by moving the code in the masquerade.module file the masquerade_user() function in the case update part of the code to the case submit part of the code. It seemed like there are times when masquerade_user() case update was called when the form data containing the users "masquerade as fields" has not been loaded in those cases the database field was cleared.

This may break other things but seems to be working for me.

case 'submit':
$old_session_id = session_id();
/* code move from case update to case submit */
if ($category == 'account') {
$users = drupal_explode_tags($edit['masquerade_users']);
db_query("DELETE FROM {masquerade_users} WHERE uid_from = %d", $edit_user->uid);
foreach ($users as $user) {
$u = user_load(array('name' => $user));
db_query("INSERT INTO {masquerade_users} VALUES (%d, %d)", $edit_user->uid, $u->uid);
}
$edit['masquerade_users'] = NULL;
}
/* end code moved */
break;

case 'update':

break;

I tried this, and it does keep existing assignments in place.

Howerver ...

It prevents new ones from being assigned.

I am closing this bug report, as Drupal 6 is no longer supported. Please re-open it if the issue is still relevant for the Drupal 7 or 8 version of the module.