Whiting out is better than putting 0, or even worse, 00.
You put a zero on a quantity if it's very unusual that this quantity is zero. Skills don't qualify for this.
If it's common to have nothing of X, you remove X from the visual listing, to declutter the listing. You may leave an empty space in place of X, because people are used to search for X in a certain place. Digits attract attention, but an empty skill should not attract attention. Instead, the only skills remaining need attention.
The possibility of picking up skills doesn't affect this. You can go back from whited-out to showing nonzero. Whiting it out is good.
-- Simon