Realex payment gateway undefined index errors

When using the Realex Payments gateway for donation and other contribution forms, the following errors or warnings appeared:

Notice: Undefined offset: 1 in setRealexFields() (line 332 of sites/all/modules/civicrm/CRM/Core/Payment/Realex.php) [note: when amount entered was $10]
Notice: Undefined index: issue_number in setRealexFields() (line 386 of sites/all/modules/civicrm/CRM/Core/Payment/Realex.php)
Notice: Undefined index: credit_card_start_date in setRealexFields() (line 399 of sites/all/modules/civicrm/CRM/Core/Payment/Realex.php)

Note, the last 2 errors only appear if you enter in a credit card number, rather than debit card, where there is no issue number and start date to enter necessarily.

Attached patch fixes these errors for me.

FYI, I'm using Drupal 7, CiviCRM 4.1.5, PHP 5.3.10