If I use Cramorant V's "Beak Catch" attack, can I choose to fail to get any cards from my deck?
Only if there are no cards left in your deck. Since you can get any type of card, and it is known that you have cards in your deck, you must take at least 1 card if you are able to.
Source: Sword & Shield FAQ (2020-01-24), TPCi Rules Team (2020-02-06)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH1_155
SWSH1_155
SWSH1_198
SWSH1_198