Based on this ruling
viewtopic.php?f=59&t=77143
Does that mean that I can play Failure of Courage in a battle where my opponent doesnt have presence?
Failure of Courage
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Yes, you can take the Battle action on Failure of Courage if you are the Defender and you control an unopposed unit at the current battlefield. All its effects fail so the action is not successful.