Uncaught exception in GWT after http request

I have an web application created with GWT which interacts with a server via http requests to php files. I make a request to the following php file: http://localhost/bibliotheek/php/addUser.php?username=username.test2&group=test&admin=false&password=&topadmin=false

When I do this in hosted mode (so after compiling) I get the following exception:

uncaught exception: [Exception... "'java.lang.NumberFormatException: For input string: ""' when calling method: [nsIDOMEventListener::handleEvent]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "JS frame :: chrome://firebug/content/spy.js :: callPageHandler :: line 744" data: no]

Line 0

I get this exception only with this request, not with other requests. I make the request with the following code:

protected void addUserToTheDatabase(String[] data) {


    String file = "addUser.php?username=" + data[0] + "&group=" + data[1] + "&admin=" + 
                  data[2] + "&password=" + data[3] + "&topadmin=" + data[4];

    request object = new request(); 
    object.getMessageXml(file, "GET", "null", new AsyncCallba开发者_开发技巧ck<String>() {

        @Override
        public void onFailure(Throwable caught) {
            new UserInterface.notification(BibPhp.error.INTERNET_CONNECTION);   
            caught.getMessage();
        }

        @Override
        public void onSuccess(String result) {

            if(Integer.parseInt(result) == 0) {
                new UserInterface.notification("Deze gebruikersnaam is reeds in gebruik.");
            }
            else {
                new UserInterface.notification("Gebruiker toegevoegd.");
            }
            new add(false);
        }
    });
}

I have no idea what I do wrong because all the other requests or exact the same, just to an other file. The php file doesn't generate a a response, so that can make any influence.

Any other people that experienced this problem or any suggestions?

Thanks in advance.

---

In your onSuccess method you do an Integer.parseInt(result). If the value of result is "" you might get the above exception. I would confirm that the value of result is actually a number and not an empty string. You can also put a try ... catch around the parseInt call to catch the NumberFormatException and notify the user.