We have 2 price levels for our events: adult and child but cannot make either of them required as it is possible in our case to register either a child, or an adult. We use the numeric/quantity fields. Some people hit "register" without filling in anything and get through to the confirmation screen. In the back-end the registration shows up with a "registered" status and "attendee" role and payment amount "$0". How can this be prevented?
Joomla 3.4.8 CiviCRM 4.6.10
I'm not allowed to post more than 1 image so here's the back-end: