//CRM-13420
if (empty($defaults['payment_instrument_id'])) {
$defaults[$form->_pId]['payment_instrument_id'] = key(CRM_Core_OptionGroup::values('payment_instrument', FALSE, FALSE, FALSE, 'AND is_default = 1'));
//CRM-13420
if (empty($defaults['payment_instrument_id'])) {
$defaults[$form->_pId]['payment_instrument_id'] = key(CRM_Core_OptionGroup::values('payment_instrument', FALSE, FALSE, FALSE, 'AND is_default = 1'));