Create discount transaction fails for event price sets that do not use radio buttons

I created an Event price set with 2 SELECT fields (see screenshot). When I do online registration, I get this notice on the Thank-you page:

Notice: Undefined index: amount_priceset_level_radio in CRM_Event_Form_Registration_Confirm::processContribution() (line 991 of /Users/dgg/git/crm_v4.3/CRM/Event/Form/Registration/Confirm.php).

I did a dump of the $params array above that line (screenshot attached) and instead of the expected 'amount_priceset_level_radio' element, I have 'amount_priceset_level_select'. The code needs to be refactored to handle the fact that the price set will not always have a radio button as it's first field (or at all). With the current code - the call to CRM_Event_BAO_Participant::createDiscountTrxn fails.