fix post endpoint

race/src/main/java/cz/muni/pa165/race/service/RaceService.java

@@ -48,6 +48,14 @@ public class RaceService implements RaceServiceI {
   @Transactional
   public RaceDto postRace(RaceDto raceDto) {
     raceDto.setId(null);
+
+    if (raceDto.getDriverOne() != null && raceDto.getDriverOne().getDriverId() != null) {
+      dbGetter.getDriver(raceDto.getDriverOne().getDriverId());
+    }
+    if (raceDto.getDriverTwo() != null && raceDto.getDriverTwo().getDriverId() != null) {
+      dbGetter.getDriver(raceDto.getDriverTwo().getDriverId());
+    }
+
     return convertRace(raceRepository.save(convertRaceDto(raceDto)));
   }