ActionHandler wrong to set content length on answerJSON

AbstractChangeRequestActionHandler

protected void answerJSON(int status, Map<String, String> answer) throws IOException
{
    ObjectMapper mapper = new ObjectMapper();
    XWikiContext context = contextProvider.get();
    XWikiResponse response = context.getResponse();
    String jsonAnswerAsString = mapper.writeValueAsString(answer);
    response.setContentType("application/json");
    // cause by 
    response.setContentLength(jsonAnswerAsString.length());
   // when comments or jsonAnswerAsString.getBytes(context.getWiki().getEncoding()).length works well   

    response.setStatus(status);
    response.setCharacterEncoding(context.getWiki().getEncoding());// Default UTF8
    response.getWriter().print(jsonAnswerAsString);
    context.setResponseSent(true);
} 

if answer has UTF8 characters. ContentLength is not enough to response data.

Reproduction steps:

• XWiki support multiple languages with ChangeRequest supported de/fr/ja
• ChangeRquest Configuration check "ONLY ACCEPT APPROVERS THAT HAVE THE APPROVAL RIGHT"
• Open a new change request and the approvers group set XWikiAllGroup
• Save it will check the approval right and response "changeRequestError" with translation "changerequest.checkers.approversright.incompatibilityReason"
• UI show the otherError
  
• Change the language to de and save again.
• UI now not show other error.

Expected result:

• Correct response data

Obtained result:

• Response data was truncated，ajax callback not resolve, ui not show the otherError.

  {"changeRequestError":"Der gewählte Genehmigende hat nicht die richtigen Rechte für die Genehmigung.