Given the latest FAQ (1.6+), and the attempt at clarifying how MUST X OR Y means player must try to do X, and if he/she could not, do Y (v.s. MUST EITHER X OR Y giving player the choice)...

Quest 1B of blood of gondor: "at the beginning of the combat phase, each player MUST turn each of his hidden cards faceup, OR take 1 hidden card"

What if I have no hidden cards; does it result in nothing (I turned up my zero cards) or taking a hidden card? (I could NOT do X, I MUST do Y)?

In general I would also like it if someone could point me to clarifications about this whole MUST, OR with respect to what counts as doing X. For example:

"Must pay 2 resources OR Y":

If I have one resource: must I still lose it, THEN fail to do X and thus do Y?