Cannot 'change selections' if no selections were made initially

In the fringe case where:

• There is an event with a price set, but no fields are 'required'
• A participant registers online without selecting any price fields

Then:

• The 'Change selections' options does not appear when editing the participant record, so no selections can be added via back office

Fix: Minor template adjustment to display the 'Change selections' link, even when no selections have been made (but still only for 'paid' events).