OZG-4949 Handle null ConstraintViolation

src/main/java/de/ozgcloud/admin/common/errorhandling/ExceptionController.java

@@ -25,6 +25,7 @@ import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 
 import jakarta.validation.ConstraintViolation;
@@ -69,18 +70,20 @@ public class ExceptionController extends ResponseEntityExceptionHandler {
 	public ErrorResponse handleConstraintViolationException(ConstraintViolationException ex) {
 		var problemDetail = ProblemDetail.forStatusAndDetail(HttpStatus.UNPROCESSABLE_ENTITY, ex.getLocalizedMessage());
 
-		problemDetail.setProperty("invalid-params", getDetailedviolationList(ex.getConstraintViolations()));
+		problemDetail.setProperty("invalid-params", getDetailedviolationList(Optional.ofNullable(ex.getConstraintViolations())));
 		return ErrorResponse.builder(ex, problemDetail).build();
 	}
 
-	private List<Map<String, String>> getDetailedviolationList(Set<ConstraintViolation<?>> violations) {
+	private List<Map<String, String>> getDetailedviolationList(Optional<Set<ConstraintViolation<?>>> violations) {
 		List<Map<String, String>> detailedViolations = new ArrayList<>();
-		for (var violation : violations) {
+		if (violations.isPresent()) {
+			for (var violation : violations.get()) {
 				var detailedViolation = new LinkedHashMap<String, String>();
 				detailedViolation.put("name", violation.getPropertyPath().toString());
 				detailedViolation.put("reason", violation.getMessage());
 				detailedViolations.add(detailedViolation);
 			}
+		}
 		return detailedViolations;
 
 	}