The real question is whether the late arrival of the Dubrovnik flight made the connection less than the minimum time allowed for this particular airport or not. In other words, say, the minimum allowed connection time for FRA is 1 hr. If your original scheduled connection time was 1,5 hour and Croatian made it 30 minutes (less than the allowed minimum for this particular airport) it's their fault and you are entitled to compensation. If you original scheduled connection time was 2,5 hours and and the late arrival of your first flight made it 1,5 hours (still more than allowed minimum) than it's your fault and Croatian owes you nothing.