Thank you for voting!
A lot of European elections have huge numbers of blank ballots...that is, people don’t vote for any candidate or party, since generally they don’t have a write-in there...while if they had actually voted, even if the candidate or party weren’t perfect, it could have changed the course of history for their country. So you’ve helped to change ours!
A really dumb way to protest, a blank ballot just allows someone else to mark it for you. If you truly can't chose, then mark both candidates which would prevent someone else picking one or the other for you.