// wicket bit too flexible, wicket internally created errors are not just Strings
// but if you added an error using the error(String) signature - will be just String
if(fm.getMessage() instanceof String) {
message = (String) fm.getMessage();
} else {
ValidationErrorFeedback error = (ValidationErrorFeedback) fm.getMessage();
message = error.getMessage();
}
if(!previous.contains(message)) {
previous.add(message);
return true;
}