We have a contribution page with the option to mark the donation as recurring with the ability to specify the term (how many months). This was working well, until recently, we are receiving a big red notice at the top of the page, even though the contribution appears to have registered correctly with CiviCRM as well as with Paypal. Here's the error:

Notice: Undefined index: installments in CRM_Core_Payment_PayPalImpl->doDirectPayment() (line 371 of /[PATH_TO_CIVI]/crm/sites/all/modules/civicrm/CRM/Core/Payment/PayPalImpl.php).

Any ideas as to what I need to do to make this error/notice go away?

EDIT: I checked line 371 in the file specified and this is the line:

 $args['totalbillingcycles'] = $params['installments'];

Which exists in the middle of the following If statement starting on line 356:

if (CRM_Utils_Array::value('is_recur', $params) == 1) {
      $start_time = strtotime(date('m/d/Y'));
      $start_date = date('Y-m-d\T00:00:00\Z', $start_time);

      $args['PaymentAction'] = 'Sale';
      $args['billingperiod'] = ucwords($params['frequency_unit']);
      $args['billingfrequency'] = $params['frequency_interval'];
      $args['method'] = "CreateRecurringPaymentsProfile";
      $args['profilestartdate'] = $start_date;
      $args['desc'] = "" .
        $params['description'] . ": " .
        $params['amount'] . " Per " .
        $params['frequency_interval'] . " " .
        $params['frequency_unit'];
      $args['amt'] = $params['amount'];
      $args['totalbillingcycles'] = $params['installments'];
      $args['version'] = 56.0;
      $args['PROFILEREFERENCE'] = "" .
        "i=" . $params['invoiceID'] . "&m=" . $component .
        "&c=" . $params['contactID'] . "&r=" . $params['contributionRecurID'] .
        "&b=" . $params['contributionID'] . "&p=" . $params['contributionPageID'];
    }

Any thoughts?