User Restrictions Error in ms_coupons.module

We just setup our first coupon for a membership product and on checkout received the error: 'Your user ID is not allowed to use this coupon.'

The coupon module allows you to set "User Restrictions" so that only particular usernames can use the coupon. We were not using this feature, but the module was saving blank 'User' data each time we saved the form which was causing the error.

Line 497:
foreach ($form_state['values']['users'] as $username) {
$data['users'][] = $username;
}

We changed this to:
foreach ($form_state['values']['users'] as $username) {
if (trim($username) != '') {
$data['users'][] = $username;
}
}

This resolves the error for us with no loss in the intended functionality of the feature.

Can someone please test this on their setup?

Thanks,
Rachel